IC-NRLF 


BLACK  HILLS 

(  SOUTH  DAKOTA 


PAPERS  READ  BEFORE  THE  BLACK  HILLS  MINING  MEN'S 
ASSOCIATION  AT  THEIR  REGULAR  MONTHLY  MEETINGS, 
ON  MINING  AND  METALLURGY  OF  BLACK  HILLS  ORES, 
TOGETHER  WITH  A  BRIEF  OUTLINE  OF  THE  MINING  IN- 
DUSTRY OF  THE  BLACK  HILLS  AND  SOME  STATISTICS  RE- 
LATING TO  THE  OUTPUT  OF  GOLD  FROM  THE  DISTRICT. 


1904 


PRICE    TWENTY-FIVE  CENTS. 


Copyrighted   by   fihe   Black   Hills   Mining   Men's  Association 


PAPERS  READ  BEFORE  THE  BLACK  HILLS  MINING  MEN'S 
ASSOCIATION  AT  THEIR  REGULAR  MONTHLY  MEETINGS, 
ON  THE  MINING  AND  METALLURGY  OF  BLACK  HILLS  ORES, 
TOGETHER  WITH  A  BRIEF  OUTLINE  OF  THE  MINING  IN- 
DUSTRY OF  THE  BLACK  HILLS,  AND  SOME  STATISTICS 
RELATING  TO  THE  OUTPUT  OF  GOLD  FROM  THE  DISTRICT. 


Published  under  the  Direction  and  Supervision  of  the 
Black  Hills  Mining  Men's  Association. 


COMMITTEE  IN  CHARGE: 

W.  J.  THORNBY.  A.  J.  SIMMONS. 

P.  A.  GUSHURST.  W.  S.  ELDER. 

JOHN  A.  BLATT.  S.  W.  RUSSELL. 


Copyrighted  by  the  BlackiHiMq  4VI\ning  Men^s  Association. 


1904 


OMAHA    PRINTING   COMPANY,   OMAHA 


OFFICERS  AND  BOARD  OF^JDIRECTORS 

OF 
BLACK  HILLS  MINING  MEN'S  ASSOCIATION. 


BURDETTE  MOODY,  M.  E.,  Lead,  S.  D.,  President. 

JOHN  A.  BLATT,  Vice-President. 

OTTO  P.  TH.  GRANTZ,  Second  Vice-President  and  Treasurer. 

J.  E.  PILCHER,  Third  Vice-President. 

J.  W.  FREEMAN. 

GEORGE  S.  JACKSON. 

JOHN  GRAY. 

DR.  ROBERT  L.  SLAGLE. 

JOHN  BLATCHFORD. 

WILLIAM  LETSON,  Dead  wood,  S.  D.,  Secretary. 


INDEX. 

PAGES 

Officers  and  Board  of  Directors 2 

Preface    4 

Article  by  A.  J.  Simmons 6  to     12  inclusive 

"        u  Bruce  C.  Yates 14  to    32        " 

"  C.  W.  Merrill 33  to    46        " 

"  Chas.  H.  Fulton 47  to    61 

"  John  M.  Henton 63  to    68        " 

"  John  Gross 69  to    81 

"  John  T.  Milliken 82  to    96 

"  John  Randall 97  to  103 

"  Dr.  Franklin  R.  Carpenter 104  to  108 

'•  Paul  Danckwardt 110  to  114        " 

"  John  Blatchford ...116  to  118 

•'  Cleophas  C.  O'Harra 119  to  127        " 

'•  Dr.  J.  E.  Todd..  .  128  to  136        " 


ILLUSTRATIONS. 

PAGE 

South  Dakota  Gold  Mill,  Worlds  Fair  Grounds,  St.  Louis .5 

Horseshoe  Mining  Co.'s  Mill 9 

Hidden  Fortune  Mill 13 

Illustration  No.  1  and  View  of  Lead,  S.  D  . . . . 17 

Interior  of  Homestake  Cyanide  Mill,  Lead,  S .  D 22 

Ellison  Hoisting  Works  of  Homestake  Mining  Co.,  Lead,  S.  D 29 

Homestake  Cyanide  No.  1  in  Lead  S.  D 35 

Homestake  Cyanide  No.  2  in  Blacktail,  S.  D 37 

Figure  No.  1 ' 39 

Figure  No.  2 43 

Wasp  -No.  2  Mining  Go's  Mill . .  49 

Dead  wood  Standard  G.  M.  &  M.  Go's  Mill  at  Cyanide,  S.  D 53 

Dakota  Mining  Company  Mill  in  Deadwood,  S.  D 56 

Lundberg,  Dorr  &  Wilson  Mill,  Terry,  S.  D  . . 62 

Maitland  Mill  and  Hoist,  Maitland,  S.  D 79 

Imperial  Mining  Company's  Mill  in  Deadwood,  S.  D 84 

Cyanide  Mills  of  the  First  Ward  in  Deadwood,  S.  D 88 

Lexington  Hill  Gold  M.  &  M.  Company's  Mill,  Spruce  Gulch,  S.  D 99 

Golden  Reward  Smelter,  Deadwood,  S.  D 109 

Golden  Reward  Cyanide  Plant,  Deadwood,  S.  D 115 

Clover  Leaf  Mining  Company's  Mill,  Roubaix,  S.  D 121 

Plant  of  the  Spearfish  Reduction  Company,  Cyanide,  S.  D 125 


333083 


PREFACE. 


On  September  3rd,  1901,  the  Black  Hills  Mining  Men's  Association  was 
organized,  having  in  view  the  advancement  of  the  mining  industry  of  the 
Black  Hills  of  South  Dakota,  the  cultivation  of  a  better  feeling  among  the 
mining  men  of  the  district,  and  the  advertising  to  the  world  of  the  vast 
mineral  resources  of  what  has  been  described  as  "the  richest  100  miles 
square  in  the  world." 

No  definite  plan  was  outlined  for  this  work,  but  as  the  association  grew 
in  numbers  and  strength,  its  field  of  work  developed  accordingly.  The  first 
thought  of  its  organizers  was  to  get  accurate  and  reliable  information  about 
the  vast  mineral  resources  of  the  Hills,  the  different  characters  of  ore,  the 
methods  that  were  being  adopted  for  the  treatment  of  the  same,  and  to  get 
this  information  in  a  concise  form  for  distribution. 

About  that  time  the  immense  bodies  of  low  grade  ore  found  in  the 
Black  Hills — and  which  have  caused  the  Hills  to  be  known  as  the  greatest 
low  grade  mining  district  of  the  world — began  to  attract  attention.  These 
ores  were  found  to  be  well  adapted  to  cyanidation  and  new  plants  sprung 
up  everywhere.  An  army  of  chemists,  old  and  young,  became  interested 
at  once  in  this  method  of  treating  ores,  and  set  their  brains  to  work  to  see 
to  what  extent  the  process  could  be  developed  in  the  treatment  of  the  ores. 
It  is  conceded  that  this  process  is  more  widely  used  in  the  Black  Hills  than 
in  any  other  mining  district.  Several  of  the  papers  in  this  book  are  upon 
the  cyanide  process  as  it  is  applied  in  the  different  mills  of  the  Black  Hills. 
These,  and  other  papers  were  read  before  the  association,  and  created  a 
widespread  interest,  not  only  in  the  process,  but  also  in  the  meetings  of  the 
association.  A  number  of  these  papers  have  been  published  in  pamphlet 
form  and  distributed  all  over  the  world.  Calls  for  them  have  been  received 
from  South  Africa,  Australia,  Central  America,  and  from  other  mining 
localities  where  cyanidation  is  only  in  its  infancy.  It  has  been  thought 
desirable  to  publish  these  papers,  together  with  the  others  that  are  con- 
tained herein,  in  one  small  book,  for  general  distribution,  on  the  ground 
that  it  will  be  more  likely  to  furnish  the  kind  of  information  desired  by 
mining  men.  We  have  added  a  brief  outline  of  the  mining  industry  of  the 
Black  Hills,  and  also  give  some  statistics  showing  the  output  of  gold  from 
the  Hills  and  the  new  reduction  plants  under  headway. 

The  committee,  on  behalf  of  the  association,  desires  to  acknowledge 
its  indebtedness  to  the  gentlemen  whose  papers  have  been  published,  for 
permission  to  publish  them  in  this  form. 


MINING  AND  MILLING  IN  THE  BLACK  HILLS. 

BY  MAJOR  A.  J.  AND  JESSE  SIMMONS. 

There  are  two  distinctive  features  of  Black  Hills  mining  that  place 
it  apart  from  any  other  section  on  earth.  They  are  the  immense  bodies  of 
ore  and  the  scientific  methods  employed  in  their  mining  and  milling.  The 
extent  of  these  ore  bodies  can  hardly  be  conjectured.  They  have  been 
identified  at  dozens  of  places,  and  the  limits  have  many  times  been  estab- 
lished by  theorists.  But  such  limits  have  been  as  promptly  extended  by 
exploration  and  the  opening  of  new  camps.  Some  writer  has  said  of  the 
Black  Hills  that  "every  hill  contains  a  gold  mine."  The  truth  of  this  asser- 
tion, while  it  may  sound  rather  broad,  is  daily  brought  home  more  forcibly 
upon  the  report*  of  new  discoveries.  Had  the  writer  continued  his  theme 
one  point  farther  he  would  have  said  that  "every  gulch  contained  a  gold 
mill." 

And  it  is  in  these  mills  that  the  free-milling  and  cyaniding  processes 
have  been  advanced  to  the  highest  stage  of  perfection  known  to  the  mining 
fraternity.  The  Black  Hills  challenges  the  world  to  compete  with  its  mill 
practices.  It  is  at  the  Homestake  that  ore  reduction  and  amalgamation 
has  been  constantly  improved  for  the  past  quarter  of  a  century  until  today 
hydrometallurgists  the  world  over  are  striving  to  reach  the  mark  set.  In 
the  cyanide  mills  a  revelation  has  been  made  to  the  world  in  the  economical 
handling  of  ores.  Even  South  Africa  with  its  Kaffir  labor  at  25  cents  a  day 
cannot  treat  ores  by  cyanide  as  cheaply  as  the  Black  Hills,  where  the  stand- 
ard of  wages  is  $3.00  a  day.  The  Homestake  tailings  cyanide  mills  are 
known  and  spoken  of  as  remarkable  plants  wherever  mining  is  conducted. 
They  are  remarkable  as  to  size  and  treatment  costs.  One  has  a  capacity 
of  1,800  tons  per  day  and  another  treats  1,000  tons  every  twenty-four  hours. 
Costs  average  28  cents  per  ton.  The  nearest  approach  to  this  figure  is  on 
the  Rand,  but  there  the  cost  is  nearly  double,  or  53  cents  per  ton.  And  in 
the  cyanide  mills  handling  raw  ore  as  it  comes  from  the  mines  records  have 
been  made  which  have  never  been  approached  outside  of  the  Hills.  The 
Deadwood  Standard  has  mined,  milled,  paid  all  office,  general  and  inci- 
dental expenses  at  the  unprecedented  figure  of  $1.22  per  ton.  The  Wasp 
No.  2  mill  was  operated  one  month  on  ore  assaying  $1.60  a  ton,  and  at  the 
end  of  the  month  paid  a  small  dividend. 

It  must  not  be  understood  that  all  Black  Hills  mines  operate  as  cheaply 
as  the  three  mentioned,  Homestake,  Deadwood  Standard,  and  Wasp  No.  2. 
They  are  peculiarly  endowed  with  physical  conditions  which  tend  to  greatly 
lessen  operating  expenses.  In  the  latter  two  the  ore  is  virtually  quarried, 
and  is  of  a  character  allowing  coarse  crushing  and  cheap  treatment.  In 
the  Homestake  the  enormous  size  of  the  ore  bodies  and  the  stoping  system 


Black  Hills  Mining  Men's  Association. 


applied  thereto  at  once  make  operations  cheap,  for  that  peculiar  ratio 
applied  to  all  manufacturing  businesses  is  true  of  mining,  viz:  increased 
output  cheapens  cost. 

Aside  from  the  Homestake,  where  the  recovery  averages  for  years  at 
a  time,  $3.54  to  $5.00  per  ton,  the  average  gold  values  saved  per  ton  is  from 
$5.00  to  $8.00.  And  it  is  upon  the  handling  of  these  grades  of  ore  that  the 
Black  Hills  has  built  up  an  industry  which  places  it  far  in  the  lead  of  all 
mining  districts.  The  enormous  bodies  of  ore,  admitting  of  cheapest  mining, 
and  the  remarkable  adaptation  of  recovery  methods  have  made  the  trans- 
mutation of  wealth  from  nature's  storehouses  in  this  section  the  marvel 
of  the  mining  industry. 

The  following  list  of  Black  Hills  mills,  writh  their  monthly  tonnages 
and  treatment  methods,  gives  an  idea  of  the  size  to  which  the  industry  has 
grown: 

STAMP-AMALGAMATION  MILLS.      Monthly  Capacity. 

Tons. 

Homestake.  . 120,000 

Clover  Leaf 7,500 

Apex 7,500 

Pluma 3,600 

Mainstay .'...; 3,600 

Golden  Empire 3,000 

Holy  Terror .  2,400 

Moritezuma 1,200 


St.  Elmo 
Clara  Belle. 
Extreme.  . 
Tykoon.  .  . 
Sunbeam.  . 

Inca 

Highland. 


,200 
,200 
,200 
,200 
,200 
,200 
,200 

Golden  Slipper 1,200 

Cochran  Mine 600 

Black  Eagle 600 

Golden  West 360 

CYANIDATION  MILLS. 

Horseshoe 15,000 

Hidden  Fortune ...... 9,000 

Spearfish 7,950 

Golden  Reward ,;.  5,250 

Jupiter ' 4,500 

Wasp  No.  2 4,450 

Deadwood  Standard 4,450 

Imperial 4,000 

Maitland 3,600 

Dakota 3,150 

Lexington  Hill 3,000 

Columbus 2,400 

Alder  Creek 2,400 

Lundberg,  Dorr  &  Wilson 2,250 

Golden  Crest .- 1,500 

Cleopatra 1,500 


Black  Hills  Mining  Men's  Association. 


PYRITIC    SMELTERS.  Mont  hly^Capacity. 

Golden  Reward 15.000 

National 7,500 

TIN  CONCENTRATORS. 
Tinton 3,000 

Total 259,860 

UNDER  CONSTRUCTION. 

Branch  Mint,  cyanide 27,000 

Gilt-Edge  Maid*,  cyanide 4,500 

Golden  West,  amalgamation 3,000 

Ruberta,  amalgamation 1,500 

Puritan,  concentration 1,500 

Grand  Total 297,360 

These  mills  are  not  now  all  in  full  commission  and  probably  never  were 
all  at  any  one  time — the  exigencies  of  the  mining  business  are  the  same  as 
that  of  others.  There  are  occasional  stoppages  in  whole  or  in  part,  repairs 
have  to  be  made,  accidents  will  occur,  etc.,  and  probably  a  fair  conservative 
estimate  on  the  actual  annual  tonnage  of  ores  treated  in  the  Black  Hills 
mills  would  approximate  about  2,000,000  tons.  This  is  steadily  and  con- 
stantly increasing. 

The  amalgamation  plants  are  headed  by  the  Homestake,  the  greatest 
gold  mine  in  the  world,  which,  with  its  1,000  stamps  reduces  daily  4,000 
tons  of  ore.  Following  the  amalgamation  the  coarser  portions  of  the  tail- 
ings are  treated  by  cyanidation. 

The  Homestake  is  called  the  greatest  gold  mine  in  the  world  for  several 
apparent  reasons.  It  has  not  missed  paying  a  monthly  dividend  for  twenty- 
five  years  and  seven  months,  and  during  that  time  it  and  the  Caledonia, 
Deadwood-Terra  and  DeSmet  Companies,  all  now  amalgamated,  have  paid 
$20,000,000  in  dividends,  and  produced  $90,000,000.  It  has  the  greatest 
annual  production  of  any  gold  mine,  namely,  $4,500,000  per  annum.  It  has 
today  in  sight  in  its  mines  enough  ore  to  supply  its  present  capacity  for 
twenty  years,  and  this  at  only  1,100  feet  depth.  Practically  no  ore  has 
been  removed  below  800  feet  except  as  taken  out  in  the  course  of  driving 
development  drifts  and  cross  cuts,  while  there  are  millions  of  tons  as  yet 
untouched  above  that  level.  On  the  lower  levels  the  ore  body  is  500  feet 
wide.  From  north  to  south,  over  two  miles,  the  ore  is  obtained  from  numer- 
ous open  cuts,  shafts  and  tunnels. 

All  of  this  has  been  accomplished  upon  the  handling  of  ores  from  which 
are  recovered  $3.50  to  $5.00  per  ton,  and  the  wonder  of  it  is  that  it  has  been 
done.  Besides  disbursing  $20,000,000  to  its  stockholders,  the  Homestake 
Mining  Company  has  earned  and  expended  many  other  millions  of  dollars 
in  betterments  and  expansion  of  its  territory.  It  has  grown  from  less  than 
ten  acres  to  over  2,600;  its  milling  equipment  increased  from  eighty  to 


10  Black  Hills  Mining  Men's  Association. 

1,000  stamps;  its  Ellison  and  other  hoists  built  and  equipped  at  an  expense 
of  millions  of  dollars;  its  water  system  from  Spearfish  River  completed  at 
a  cost  of  a  round  million;  all  upon  the  profits  of  an  original  investment  of 
$300,000,  which  paid  for  the  first  claim  and  furnished  the  first  mill  and  hoist. 
Thus  the  Homestake  stands  alone,  a  peerless  figure  in  the  mining  industry, 
a  living  monument  of  solidarity  dedicated  to  the  handling  of  low  grade  ores 
on  a  business  basis. 

The  Homestake  Belt  of  veins,  similar  to  the  Mother  Lode  of  California, 
has  been  traced  through  the  Hills  a  distance  of  forty  miles,  on  a  course  of 
south  thirty-five  degrees  east  from  Maitland,  through  Lead,  and  on  as  far 
as  Keystone,  and  identified  at  numerous  intervening  points.  Thus  the 
Homestake  has  not  pre-empted  the  whole  field,  but  there  is  abundant  room 
for  dozens  of  like  institutions. 

The  Clover  Leaf  Mine  at  Roubaix,  on  the  Homestake  Belt,  operates 
a  sixty-stamp  mill,  saving  values  entirely  by  amalgamation.  Late  cleanups 
show  returns  of  a  little  better  than  $6.00  per  ton,  and  at  the  deepest  work- 
ing, 700  feet,  the  grade  of  ore  is  better  than  at  any  point  previously  opened. 
Continuing  on  southward  mines  are  being  opened  and  small  mills  have  been 
built  at  frequent  points  along  the  Belt,  and  important  developments  are 
today  under  way  at  numerous  points.  At  Keystone  large  low  grade  veins 
are  identified  as  Homestake  Belt  material,  while  at  the  Holy  Terror  Mine 
an  exceptionally  rich  vein  has  been  milled  to  a  depth  of  1,200  feet.  The 
Holy  Terror  has  produced  about  $2,500,000  and  paid  $270,000  in  dividends. 
It  is  equipped  with  a  twenty-stamp  mill.  Other  mills  at  Keystone  are 
Tykoon  and  Mainstay. 

CONTACT  DEPOSITS. 

Immediately  overlying  the  Algonkian  rocks  in  which  are  found  the 
fissures  of  the  Homestake  Belt  is  first  a  bed  of  conglomerate,  next  Cambrian 
quartzite,  then  sandstone  and  shales  to  a  depth  of  200  to  300  feet.  Intru- 
sions of  porphyry,  phonolite,  trachyte,  rhyolite,  and  other  eruptive  rocks 
have  twisted  and  folded  the  formations  to  great  extent.  Mining  engineers 
agree  that  these  eruptions  have  had  great  bearing  upon  the  ore  deposition, 
and  the  miner  always  looks  for  porphyry — using  the  term  in  the  most  gen- 
eral sense — in  proximity  to  all  ore  bodies. 

The  contact  deposits  of  Bald  Mountain,  Maitland,  Yellow  Creek,  Two 
Bit,  Blacktail,  Galena,  etc.,  have  been  mined  for  the  past  fifteen  years,  and 
still  new  mines  and  new  camps  are  constantly  being  opened.  When  it  is 
considered  that  about  three  townships  in  western  Lawrence  County  are 
underlaid  by  this  formation,  and  have  scarcely  been  scratched,  the  field  is 
open  for  even  greater  camps  than  those  at  present  known.  At  first  the  ores 
were  shipped  to  Omaha,  Denver  and  elsewhere  for  smelting,  the  miners 
utilizing  only  the  high  grades.  Next  matte  smelting  was  introduced  to 
the  Hills  about  1890,  and  fifteen  to  twenty  dollar  ore  profitably  handled. 
Then  chlorination  made  pay  ore  of  ten  to  fifteen  dollar  stuff.  But  it  was 
upon  the  introduction  of  the  cyanide  process  that  mining  of  the  contact 
deposits  reached  the  height  of  its  glory.  Ores  worth  from  $2.00  to  $10.00 


Black  Hills  Mining  Men's  Association.  11 

per  ton  are  now  successfully  handled.  And  it  is  upon  the  application  of  this 
process  to  the  handling  of  the  siliceous  contact  ores  that  the  greatest  industry 
of  the  Hills,  aside  from  the  mining  of  the  free-milling  belt,  is  established. 

Cyanidation  has  made  available  untold  millions  of  dollars  contained 
in  these  refractory  ores.  It  has  undoubtedly  done  more  to  place  the  Black 
Hills  in  the  front  rank  of  mining  communities  than  any  other  single  factor. 
And  its  adaptations  as  observed  in  the  Hills  are  studied  by  mining  men  the 
world  over.  The  Black  Hills  Mining  Men's  Association  is  the  forum  of 
experimentation  and  publicity  of  mill  practice.  The  papers  read  before  it 
and  published  in  this  volume  embody  data  on  the  practical  operation  and 
results  of  mill  superintendents  in  cyanidation  in  the  district.  They  may  be 
said  to  form  the  classics  of  our  knowledge  of  cyanidation. 

The  list  of  cyanide  plants  of  the  Black  Hills  as  previously  given  includes 
first,  the  Horseshoe,  the  largest  complete  wet  crushing  cyanide,  plant  in  the 
world.  Its  120  stamps  have  a  capacity  of  500  tons  of  raw  ore  per  day.  It 
is  a  model  in  every  particular. 

Continuing  down  the  list  are  such  mills  as  Golden  Reward,  Hidden 
Fortune,  Spearfish,  Jupiter,  Wasp  No.  2,  Deadwood  Standard,  Imperial, 
Maitland,  Dakota,  Lexington,  Lundberg,  Dorr  &  Wilson,  etc.,  all  distinc- 
tive in  a  way,  and  yet  all  operating  successfully  on  the  great  contact  deposits 
of  low  grade  ores. 

Spearfish  and  Deadwood  Standard  handle  ore  from  the  carboniferous 
lime  formation,  and  during  the  past  two  years  have  paid  $123,000  in  divi- 
dends. Both  are  plain  types  of  dry,  coarse  crushing  mills.  The  porous 
character  of  the  ore  admits  of  coarse  crushing  and  quick  extraction  is  accom- 
plished. 

Under  the  head  of  tin  concentrators  the  Black  Hills  offers  to  the  in- 
spection of  the  world  the  only  producing  tin  mine  on  the  American  conti- 
nent. The  plant  has  a  capacity  of  100  tons  daily,  crushing  with  rolls  and 
concentrating  on  Bartlett  tables.  The  cassiterite  concentrates,  for  the  time 
being,  are  shipped  to  Swansea  for  smelting.  The  vein  is  in  the  igneous  for- 
mation (granite  and  porphyry)  and  is  disclosed  in  the  workings  100  feet  wide, 
and  its  out-crop  identified  for  several  miles.  Adjoining  companies  are 
watching  operations  closely  and  more  plants  of  a  similar  character  are  an- 
ticipated, as  this  mill  is  opening  the  road  to  success. 

But  after  all  the  Black  Hills  is  a  great  low  grade  gold  field,  where  illimit- 
able quantity  compensates  for  high  values  and  resolves  mining  to  a  perma- 
nent industry — its  ore  supply  will  last  for  ages.  The  treatment  of  the  im- 
mense deposits  requires  careful  management,  large  milling  facilities  and 
economic  mining  and  handling  of  the  ore.  The  Hills  is  endowed  with  phys- 
ical advantages  second  to  no  mining  district  on  earth.  Timber,  water  and 
railroad  communications  are  par  excellence,  its  climate  agreeable,  and  lastly, 
it  is  within  easy  reach  of  eastern  money  centers.  One  has  but  to  peruse  the 
list  of  plants  under  construction — a  sample  of  a  year's  growth  of  this  won- 
derful mining  district — to  form  an  idea  of  the  future  possibilities  of  the  coun- 
try. Its  growth  is  natural  and  steady,  and  one  day  it  will  be  known  as  the 
world's  greatest  gold  producing  camp. 


12  Black  Hills  Mining  Men's  Association. 


SOUTH  DAKOTA  GOLD  PRODUCTION. 

According  to  Hon.  Geo.  E.  Roberts,  director  of  the  U.  S.  Mint,  South 
Dakota  stands  third  on  the  list  of  gold  producing  states. 

With  the  exception  of  Alaska,  an  exclusive  placer  field,  South  Dakota's 
annual  gold  output  is  only  exceeded  by  the  great  mining  states  of  Colorado 
and  California. 

And  when  it  is  considered  that  the  gold  producing  area  of  South  Dakota 
is  confined  to  the  Black  Hills,  a  section  barely  forty  miles  wide  by  eighty 
long,  the  wonderful  resources  of  the  country  are  apparent. 

The  paraphrase  "richest  one  hundred  miles  square  in  the  world"  fit- 
tingly describes  this  wealthy  little  mountain  range  in  comparison  with  the 
hundreds  of  thousands  of  square  miles  comprising  the  great  mining  empires 
of  Montana,  Idaho,  Oregon  or  Utah. 

The  following  table  gives  the  total  gold  output  of  the  Black  Hills  since 
the  yellow  metal  was  first  mined  in  1876,  up  to  the  year  1903,  inclusive: 

Year  Total  Production 

1876 $1,200,000 

1877 2,000,000 

1878 2,250,000 

1879 2,500,000 

1880 2,650,000 

1881 • 2,550,000 

1882 : ' 2,550,000 

1883 2,525,000 

1884 2,575,000 

1885 2,750,000 

1886 3,250,000 

1887 3,420,000 

1888 3,485,000 

1889 3,550,000 

1890 3,904,160 

1891 4,619,270 

1892 5,101,630 

1893 6,750,000 

1894 6,500,000 

1895 6,800,000 

1896 6,775,000 

1897 6,524,760 

1898 6,800,000 

1899 7,000,000 

1900 7,250,000 

1901 7,400,000 

1902 7,500,000 

1903 7,829,000 

Total.  .  .   $128,008,820 


14  Black  Hills  Mining  Men's  Association. 

SOME  FEATURES  OF  MINING  OPERATIONS  IN  THE  HOME- 
STAKE  MINE,  LEAD,  SOUTH  DAKOTA. 

BY  BRUCE  C.  YATES,  M.  AM.  INST.  MIN.  E. 

[Paper  read  before  Black  Hills  Mining  Men's  Association,  January  19,  1904.] 

INTRODUCTION. 

The  Homestake  Mining  Co.,  as  it  exists  today,  is  a  consolidation  of  the 
Father  De  Smet,  the  Dead  wood-Terra,  the  Caledonia,  the  Highland  and  the 
Homestake  Gold  Mining  Companies.  The  property  comprises  some  350 
locations  with  a  total  area  of  2,624  acres. 

The  ground  upon  which  mining  operations  are  being  carried  on  at  pres- 
ent lies  between  Deadwood  Gulch  on  the  north  and  Whitewood  Gulch  on 
the  south,  covering  about  10,000  feet  along  the  strike  of  the  ledge.  The  princi- 
pal works  and  the  offices  of  the  company  are  located  almost  in  the  heart  of 
the  town  of  Lead,  which  has  a  population  of  about  8,000.  The  town  is  built 
on  either  side  of  Gold  Run  Gulch,  which  is  a  tributary  of  Whitewood  Gulch 
and  which  passes  through  the  company's  property  from  west  to  east  a  little 
south  of  the  center. 

The  strike  of  the  Homestake  ledge  is  approximately  north  thirty-five 
degrees  west,  and  south  thirty-five  degrees  east.  The  dip  is  very  irregular. 

The  company  is  now  operating  900  stamps  and  an  additional  100  stamps 
will  be  installed  during  the  coming  year.  The  900  stamps  are  grouped  in 
six  mills,  the  Homestake  and  Golden  Star  with  200  stamps  each  and  the 
Amicus  with  140  stamps  are  located  on  Gold  Run  Gulch,  the  Pocahontas 
with  1GO  stamps  and  the  Monroe  with  100  stamps  are  located  on  Bobtail 
Gulch  which  is  a  tributary  of  Deadwood  Gulch.  The  Mineral  Point  Mill 
with  100  stamps  is  located  on  the  south  side  of  Deadwood  Gulch  and  near 
the  northerly  end  of  the  property.  The  tailings  are  treated  at  two  cyanide 
plants.  One  with  a  capacity  of  1,450  tons  per  day  is  located  on  Gold  Run 
below  the  Homestake,  Golden  Star  and  Amicus  Mills  and  treats  the  tailings 
from  these  mills.  The  other,  with  a  daily  capacity  of  800  tons,  is  located 
on  Deadwood  Gulch  at  the  mouth  of  Bobtail  and  receives  the  tailings  from 
the  Pocahontas,  Monroe  and  Mineral  Point  mills. 

The  ore  is  principally  free  milling,  seventy-two  per  cent,  being  caught 
on  the  plates,  the  total  recovery  is  approximately  eighty-eight  per  cent,  of 
the  assay  value.  (See  paper  on  Metallurgy  of  the  Homestake  Ore  by  C.  W. 
Merrill,  Met.  Eng.,  read  before  the  American  Mining  Congress  at  its  1903 
meeting  in  Lead,  S.  D.) 

The  main  source  of  the  water  supply  is  the  head  waters  of  Spearfish 
Creek.  A  pumping  plant  consisting  of  two  Riedler  pumps  driven  by  Com- 
pound Corliss  Engines  with  a  third  now  being  installed  is  located  near  the 
head  of  the  east  fork.  The  water  is  pumped  400  feet  to  the  top  of  the  divide 
between  Spearfish  and  Whitewood  Creeks  from  which  point  it  is  carried  by 
gravity  to  the  main  reservoir  at  Lead,  some  ten  miles  in  all. 


Black  Hills  Mining  Men's  Association. 


15 


A  very  small  volume  of  water  is  pumped  from  the  mine  considering 
that  there  are  about  forty-one  miles  of  track  now  open.  The  water  was 
formerly  taken  care  of  by  a  Cornish  pump  which  lifted  the  water  in  three 
stages  from  the  800  foot  level  to  the  surface,  until  about  two  years  ago  when 
a  Riedler  Compound  Condensing  ptimp,  with  a  capacity  of  550  gallons  per 
minute  under  a  head  of  1,200  feet,  was  installed  on  the  1,100  foot  level. 

The  underground  haulage  is  done  by  horses  and  mules.  The  horses 
seem  to  be  better  adapted  to  the  work  than  mules  and  in  consequence  there 
are  very  few  mules  left  in  the  mine.  The  cost  for  horse  haulage  is  three  cents 
per  ton  per  1,000  feet. 

A  five  ton  air  motor  has  been  ordered  and  will  be  tried  on  one  of  the 
lower  levels.  If  successful,  these  motors  will,  no  doubt,  take  the  place  of 
horses  on  all  main  haulage  ways.  A  fifteen  ton  motor  is  now  being  used  on 
the  tramway  level  to  haul  ore  from  the  crusher  bins  to  the  mills.  The  air 
is  supplied  at  a  pressure  of  950  pounds  by  a  100  horse  power  three  stage 
straight  line  compressor  which  will  serve  both  motors  temporarily. 

Following  is  the  tabulated  statement  of  the  power  required  to  carry 
on  the  different  operations: 

MACHINE  DRILLS.    ' 


MANUFACTURER'S 

NAME 

SIZE 

NO.  IN 

USE 

PURPOSE  USED  FOR 

REMARKS 

Ingersoll  
Ingersoll  
Ingersoll  

A-32-2i-in. 
B-32-2i-m. 
D-32-3f-m. 

48 
12 
30 

Block  holing. 
Upper  Levels  &  Surface 
General  Mining. 

Six  of  the  In- 
gersoll are  used 
for    Ajax    drill 

Ingersoll  

D-24-3-in. 

148 

General  Mining. 

sharpening  ma- 

Rand   

3i-m. 

2 

Shaft  Sinking. 

chines  and  two 

Leyner  

3-in. 

3 

Surface  Drifting. 

are  used  for  shop 

McKeirman  .... 

3-in. 

1 

Shop'Hammer. 

welding   in    car 

repair  shops. 

244 

ELECTRIC  MACHINERY. 


MNFS. 
NAME 

K.  W.  OR  H.  P. 

HOW  DRIVEN 

WHERE  USED 

Edison  
Westinghouse 
Edison  

Edison  
Gen.  E.  &  C.& 
C  
Roth  

8^      K.  W.  Gen. 
22      K.  W.  Gen. 
6        K.  W.  Gen. 

2  (60)K.  W.  Gen. 

2  (5)  H.  P.  Motors 
2        HP  Motors 

Connected  to  line  shaft 
Connected  to  line  shaft 
Driven   by    10   H.   P. 
Ideal  Engine  
175  H.P.  Upright  Eng 

Connected  to  mill  sh't 

Cyanide  No.  2. 
Cyanide  No.  1. 

Monroe  Mill. 
B.  &  M.  Shaft. 

Amicus  Mill. 
Homestake  Office. 

Edison  
Edison  
Brush  
Gen.  Elec  

2  (20)K.  W.  Gen. 
17^    K.  W.  Gen. 
4£      K.  W.  Gen. 
4*      K.  W.  Gen. 

Line  shaft  from  engine 
25  H.  P.  Ideal  Engine. 
Connected  to  Mill  Eng. 
10  H.  P.  Ideal  Engine 

Golden  Prospect  Shaft. 
Mineral  Pt.  Mill. 
Pocahontas  Mill. 
Pump  Station. 

16 


Black  Hills  Mining  Men's  Association. 


HOISTING  ENGINES. 


MANUFACTURER'S 

NAME 

KIND  OF  ENGINE 

H.  P. 

WHERE  USED 

Union  Iron  Works.  . 
Frazer  &  Chalmers  . 
Frazer  &  Chalmers  . 

Simple  Duplex  
Simple  Geared  Duplex.  .  .  . 
Simple  Duplex  ...    . 

1200 
150 
400 

Ellison  Hoist. 
Golden  Star  Hoist. 
B.  &  M.  Hoist 

Frazer  &  Chalmers.  . 
Frazer  &  Chalmers.  . 
Frazer  &  Chalmers.  . 

Simple  Duplex  
Simple  Geared  Duplex.  .  .  . 
Simple  Geared  Duplex.  .  .  . 

500 
150 
150 

Golden  Prospect  Hoist. 
Old  Brig. 
Golden  Gate. 

2550 

CRUSHER  ENGINES. 


MANUFACTURER'S 

NAME 

KIND  OF  ENGINE 

H.   P. 

WHERE  USED 

Frazer  &  Chalmers. 

Compound  Corliss  

250 

Ellison  Hoist. 

Frazer  &  Chalmers.  . 
Frazer  §  Chalmers.  . 
Frazer  &  Chalmers.  . 
Frazer  &  Chalmers.  . 

Simple  Corliss  
Simple  Engine  
Simple  Enigne  
Simple  Engine  

250 
200 
100 
200 

1000 

B.  &.  M.  Hoist. 
Golden  Prospect. 
Old  Brig. 
Golden  Gate. 

MILL  ENGINES. 


MANUFACTURER'S 

NAME 

KIND  OF  ENGINE 

H.    P. 

WHERE  USED 

Geo.  H.  Corliss  
Geo.  H.  Corliss  
H.  Corliss  
Frazer  &  Chalmers.  . 
Union  Iron  Works.  . 
Union  Iron  Works.  . 

Cross  Compound  
Tandem  Compound  
Simple  Corliss  
Simple  Corliss  
2  Simple  Engines  
Simple  Engine  

500 
500 
350 
350 
250 
250 

Homestake  Mill. 
Golden  Star  Mill. 
Amicus  Mill. 
Pocahontas  Mill. 
Monroe  Mill  each  125  H.  P. 
Mineral  Point. 

2200 

AIR  COMPRESSORS. 


MANUFACTURER'S 

NAME 

KIND  OF  ENGINE 

H.   P. 

WHERE  USED 

Ingersoll  Sargeant.  . 
Ingersoll  Sargeant.  . 
Ingersoll  Sargeant 

2  Stage  Compound  Corliss.  . 
3  Stage  Straight  Line  
Duplex 

1000 
100 
500 

Ellison  Hoist  Low  Pressure. 
Ellison  Hoist  High  Pressure. 
B.  &  M.  Hoist  Low  Pressure. 

Ingersoll  Sargeant.  . 

Duplex  

300 

Golden  Pros.  Hoist  L.  Pres. 

Ingersoll  Sargeant.  . 
Ingersoll  Sargeant.  . 

Single  Engine  
Single  Engine  

100 
100 

2100 

Cyanide  No.  1  L.  Pressure. 
Cyanide  No.  2  L.  Pressure. 

18 


Black  Hills  Mining  Men's  Association. 


PUMPS. 


MANUFACTURER'S 

NAME 

KIND  OF  ENGINE 

H.   P. 

WHERE  USED 

Riedler  

Compound  Corliss 

250 

Mine  —  1100  ft 

Riedler  

2  Compound  Corliss 

650 

Spearfish   Creek   each   325 

1  Holly,  2  Dean.  .  .  . 

Compound  Corliss.  .  ."  

150 

H.  P. 

Settling  Dam  each  50  H  P 

Frazer  &  Chalmers.  . 

Simple  Corliss  

250 

B.  &  M.  Shaft  Cornish 

3  Prescotts  
2Heisler  

Compound  
Triple  Expansion  

120 

80 

Cyadine  No.  1  each  40  H.  P 
Cyanide  No.  2  each  40  H  P 

1500 

MISCELLANEOUS. 


MANUFACTURER'S 

NAME 

KIND  OF  ENGINE 

H.   P. 

WHERE  USED 

Simple  Engine  

25 

Ellison  Shaft  Sinking  Eng 

Simple  Engine 

30 

\niicus    Mill    Derrick 

Simple  Engine 

100 

Machine  Shop 

Simple  Engine 

25 

Pump  Sta    Hock  Crusher 

180 

In  this  paper  no  attempt  will  be  made  to  give  more  than  a  few  facts 
in  regard  to  the  mining  operations  of  the  Homestake  Mine.  Much  of  the 
matter  contained  herein  may  sound  commonplace  to  many  experienced 
mining  men.  If  any  of  the  methods  described  are  original,  it  should  be 
borne  in  mind  that  they  have  stood  the  test  of  actual  mining  operations  in 
a  mine  where  a  large  daily  tonnage  at  a  minimum  cost  is  the  object  sought. 

Illustration  No.  1  is  a  photograph  of  some  of  the  company  buildings 
and  a  part  of  the  open  cut  at  Lead.  No.  2  is  a  view  of  the  Ellison  Hoisting 
engine.  No.  3  shows  the  sand  vats  of  Cyanide  No.  1. 

SHAETS. 

The  Homestake  Mining  Co.  is  now  operating  six  shafts,  the  Ellison, 
B.  &  M.,  Golden  Star,  Golden  Prospect,  Old  Brig,  and  Golden  Gate.  Three 
of  these,  the  Golden  Gate,  Old  Brig  and  Golden  Prospect,  have  reached  the 
800  foot  level,  while  the  Ellison,  B.  &  M.  and  Golden  Star  have  reached  the 
1,100  foot  level. 

Four  of  these  shafts  are  located  on  the  hanging  wall  side  of  the  ledge, 
one  on  the  foot  wall  side  and  one  is  sunk  in  the  ledge.  All  are  connected  by 
permanent  drifts  driven  in  the  "country"  rock. 

The  Ellison  is  a  large,  three  compartment  shaft,  two  compartments 
being  used  for  hoisting  and  one  for  ladders  and  pipes.  The  two  hoisting 
compartments  are  10x5  feet  in  the  clear.  The  third  or  ladder  compartment 
is  10x6  feet  in  the  clear.  The  Golden  Star  and  Old  Brig  each  have  three 


Black  Hills  Mining  Men's  Association.  19 

equal  compartments,  4  feet,  6  inches  by  5  feet  in  the  clear.  The  B.  &  M. 
is  similar,  with  the  exception  that  there  is  a  fourth  compartment  reaching 
the  300  foot  level  in  which  is  operated  a  third  cage.  The  Golden  Prospect 
originally  had  only  two  compartments,  one  being  9  feet,  6  inches  by  5  feet 
in  the  clear  and  the  other  being  4  inches  wider  to  provide  for  pipes.  Later 
a  third  small  compartment  was  added  from  the  500  foot  to  the  800  foot  levels, 
in  which  are  placed  the  ladders  and  pipes.  The  timbering  in  the  Golden 
Gate  shaft  is  slightly  different  from  the  other  standard  three-compartment 
shafts  but  the  dimensions  are  the  same. 

After  the  first  200  feet  from  the  surface,  the  shafts,  with  the  exception 
of  the  Golden  Star,  are  sunk  in  hard  carbonaceous  wall  slate.  The  dip  of 
the  slate  intersects  the  axis  of  the  shafts  at  angles  varying  from  sixty  to 
ninety  degrees  from  the  horizontal  which  makes  blasting  the  cut  quite 
difficult. 

During  the  early  history  of  the  Homestake  and  Associated  Mining  Com- 
panies these  shafts  were  not  connected  by  underground  workings.  Now 
each  is  a  factor  in  the  mining  operations  of  the  company  and  through  each 
is  carried  on  some  part  of  the  work  incident  to  mining  about  4,000  tons  of 
ore  each  twenty-four  hours. 

"When  sinking  is  resumed  in  any  of  these  shafts,  it  is  necessary  to  pro- 
vide hoisting  facilities  to  carry  on  this  part  of  the  work  independent  of  the 
regular  cages.  This  is  accomplished  by  using  a  small  twenty-five  horse  power 
hoisting  engine  driven  by  compressed  air,  which  is  placed  on  the  lowest 
working  level  of  the  shaft.  In  the  operation  of  this  engine,  it  has  been  found 
necessary  to  re-heat  the  air  before  it  is  used  in  the  cylinder  and  this  is  done 
by  passing  the  air  through  several  coils  of  pipe  surrounding  a  small  sheet 
iron  stove,  in  which  coke  is  used  for  fuel.  A  bucket  with  a  capacity  of  one- 
half  ton  is  used  instead  of  a  cage  to  hoist  the  rock  and  men.  No  guide  head 
is  used,  plank  being  nailed  on  the  inside  of  the  timbers  of  the  hoisting  com- 
partment to  prevent  the  bucket  striking  on  the  timbers.  A  small  sheave 
wheel  is  placed  just  above  the  station  set. 

The  men  are  well  protected  by  bulk  heads  thrown  across  the  shaft  just 
above  the  sheave  wheel  or  below  the  station  on  which  the  engine  is  located. 
The  shaft  is  sunk  200  or  300  feet  in  this  manner;  stations  are  opened  on  the 
new  levels  and  cross  cutting  is  commenced.  Drifts  are  run  to  other  shafts 
of  the  belt,  which  are  tapped  by  small  raises.  These  raises  serve  the  double 
purpose  of  providing  ventilation  and  acting  as  a  chute  through  which  the 
rock  is  dumped  as  the  sides  are  stripped  down  to  make  room  for  the  regular 
shaft  timbers. 

Miners  working  in  the  shaft  are  usually  under  contract.  The  engineers, 
landers  to  dump  the  rock  from  the  bucket  into  the  cars,  and  timbermen  are 
paid  by  the  day.  The  company  furnishes  tools  and  sharpens  drills,  the 
contractors  furnish  candles,  powder,  and  pay  for  repairs  on  machines  and 
assist  in  placing  timbers. 

The  following  condensed  statement  shows  the  number  of  men  employed, 
wages  paid,  and  the  approximate  cost  of  sinking  at  the  Ellison  shaft. 


20  Black  Hills  Mining  Men's  Association. 

The  number  of  men  employed  on  each  shift  is: 

4  Miners — Contractors. 
1  Engineer. 
1  Lander. 
1  Timberman. 

1  Carpenter,  2£  shifts  framing  one  set  of  timbers  which  provides  for 
six  feet  of  the  shaft. 

The  actual  time  consumed  in  placing  one  set  of  timbers  is  eight  hours, 
but  the  timbermen  are  kept  busy  one  shift  in  each  twenty-hour  hours  run- 
ning timber  from  the  saw  mill  and  putting  in  extra  bracing. 

The  cost  of  a  set  of  timbers  in  place  for  the  Ellison  shaft  is: 

Timber $26 . 85 

Framing  Timbers 10 . 00 

4  Miners,  1  shift @  $4 . 00 16 . 00 

1  Lander,  1  shift @     3.00 3.00 

1  Timberman,  1  shift @     4 . 00 4 . 00 

1  Engineer,  1  shift @     4 . 00 4 . 00 


Total.  ..$63.85 


Cost  per  foot 10 . 64 


The  average  progress  made  is  one  foot  in  two  shifts,  including  the  plac- 
ing of  the  timbers.  The  cost  per  foot  of  shaft,  assuming  that  the  contractors 
made  $4.00  per  shift,  which  is  the  usual  price  paid  to  shaft  men,  is  as  follows: 

8  Miners @  $4.00 $32.00 

1  Timberman @     4 . 00 4 . 00 

2  Engineers ©     4.00 8.00 

2  Landers @     3.00 6.00 

&  Set  timbers,  lumber  and  framing.  . 10 . 64 

Total $60.64 

The  Rand  machine  is  used  for  drilling,  mounted  on  a  bar.  Electric 
exploders  are  used  to  fire  the  blasts  in  all  shaft  work,  forty  per  cent,  dyna- 
mite being  used  as  in  drifting. 

Station  sets  are  from  twelve  to  sixteen  feet  high.  Two  or  three  extra 
sets  are  put  in  on  the  stations  which  serve  as  braces  to  the  long  sets  of  the 
shaft  and  support  the  roof  of  the  station. 

Formerly  all  station  floors  were  covered  with  sheet  iron.  On  all  new 
levels,  however,  the  track  rails  are  laid  to  the  edge  of  the  shaft  and  in  line 
with  the  cage  rails.  Two  tracks  are  laid  up  to  the  shaft,  one  to  each  hoist- 
ing compartment.  A  diamond  cross  over,  located  close  to  the  shaft,  per- 
mits the  loaded  cars  to  be  run  on  to  either  cage  and  the  empties  to  be  re- 
turned to  the  empty  track.  A  third  track  passes  around  the  shaft  when  the 
station  is  opened  on  both  sides.  The  cages  are  made  at  the  company's  shop 
and  are  provided  with  the  usual  safety  appliances.  All  new  cages  are  made 
with  the  chair  and  operating  level  on  the  cage,  so  that  the  cage  tender  always 
has  control  of  the  chairs.  Double  decked  cages  are  used  at  the  Ellison  shaft, 
which  carry  two  cars  on  each  deck,  the  Golden  Prospect  cage  carries  two  cars 
on  a  single  deck  and  all  other  shafts  have  small  single  decked  cages.  Skips 
have  not  been  used  in  any  shaft  now  belonging  to  the  Homestake  company. 


Black  Hills  Mining  Men' ft  Association.  21 

DRIFTING. 

Three  dimensions  are  used  for  "dead  work"  drifts,  depending  upon 
the  use  for  which  they  are  intended;  prospect  drifts  6x7  feet,  single  track 
working  drifts  7x8  feet,  double  track  working  drifts  12x8  feet. 

Prospect  drifts  are  usually  driven  under  contract,  two  men  are  em- 
ployed on  each  shift.  Each  man  is  a  party  to  the  contract.  The  miners 
car  their  own  rock,  furnish  powder,  fuse,  candles,  shovels,  and  picks  and 
pay  for  the  repairs  on  machines.  The  company  furnishes  machine  and 
drills,  lays  all  track  and  puts  in  air  pipe  as  needed.  The  price  paid  is  from 
$5.00  to  $8.00  per  running  foot,  depending  on  the  character  of  the  rock. 

No  timbering  is  required  except  in  a  few  isolated  places  where  a  soft 
seam  is  encountered  necessitating  standing  a  few  tunnel  sets. 

In  running  the  7x8  single  track  drifts  either  one  or  two  machines  are 
used  for  drilling  mounted  on  a  horizontal  bar.  The  bar  has  two  decided 
advantages  over  the  post;  namely,  the  machine  may  be  set  up  as  soon  as 
"the  blasting  is  finished  and  drilling  for  the  next  round  goes  on  while  the 
shovelers  are  removing  the  rock,  and  again  the  sides  of  the  drifts  are  carried 
much  more  evenly  than  with  the  post  which  makes  it  possible  to  lay  a  straight 
track  and  allow  ample  room  for  a  ditch  on  one  side. 

Mounting  the  machine  on  a  bar  instead  of  a  post  has  only  lately  been 
tried  in  the  Homestake  Mine  and  the  result  has  proven  very  satisfactory. 
Machine  men  say  that  it  is  easier  to  move  the  machine  from  one  position  to 
another  which  fact  is  an  advantage  to  the  miner  and  will  in  the  end  mater- 
ially advance  the  interest  of  the  company. 

The  following  tabulated  statement  shows  the  cost  of  five  feet  of  average 
7x8  feet  drift. 

1  Miner,        2  shifts,  drilling @  $3 . 50 $7 .00 

1  Helper,       2  shifts,  drilling .  .  .  .  @     3 . 00 6 . 00 

1  Miner,         1  shift,  blasting @     3 . 50 3 . 50 

1  Helper,       1  shift,  blasting @     3.00 3.00 

1  Shoveler,   2  shifts @     3 . 00 6 . 00 

Explosives,  powder,  caps  and  fuse 10.75 

Blacksmith  labor,  repairs  of  machine  and  machine  shop  labor.  4 . 85 

Total  cost  of  five  feet  of  drift ...$41.15 

Cost  per  foot 8.23 

Cost  per  ton 1 . 47 

The  above  cost  statement  does  not  include  the  cost  of  laying  track  or 
putting  in  air  pipe.  This  was  left  out  because  track  and  air  pipes  are  a  part 
of  the  permanent  improvements  of  the  mine  and  not  all  of  this  item  should 
be  charged  against  any  particular  drift. 

The  holes  are  drilled  about  six  feet  deep  and  fully  five  feet  of  ground 
is  blasted  out  with  each  round.  Ingersoll  Sergeant  rock  drills  D-24  and 
D-32  are  used  almost  exclusively  in  drifting.  These  drills  seem  to  require 
less  skill  in  manipulation,  the  repair  account  is  smaller  and  they  stand  more 
hard  knocks  than  any  machine  yet  tried.  Where  two  machines  are  used 


Black  Hills  Mining  Men's  Association.  23 

mounted  on  one  bar  one  helper,  who  receives  the  same  wages  as  the  miners, 
attends  to  both,  and  the  same  number  of  holes  can  be  drilled  in  a  little  more 
than  one-half  the  time  required  when  only  one  machine  is  used. 

The  number  of  cubic  feet  of  rock  excavated  at  each  round  is  (7x8x5 
feet),  280  cubic  feet.  Ten  cubic  feet  of  this  rock  will  weigh  one  ton,  so  that 
280  cubic  feet  equals  twenty-eight  tons.  Dividing  $41.15  by  twenty-eight 
gives  $1.47  as  the  cost  of  excavating  one  ton  of  rock  from  the  face  of  a  7x8 
foot  drift.  It  may  be  of  interest  to  note  in  connection  with  the  weight  of 
the  rock  that  the  shovelers  will  have  to  remove  from  twenty-five  to  thirty 
cars  of  broken  rock.  Homestake  Mine  cars  have  a  volume  of  twenty  cubic 
feet.  This  would  indicate  that  the  volume  increases  100  per  cent. 

Tabulating  the  cost  of  double  track  12x8  foot  drifts  in  a  similar  manner 
gives  the  following: 

1  Miner,        3  shifts,  drilling @  $3 . 50 $10 . 50 

1  Helper,      3  shifts,  drilling @     3 . 00 9 . 00 

1  Miner,         1  shift,  blasting.  . @     3 . 50 3 . 50 

1  Helper,       1  shift,  blasting @     3 . 00 3 . 00 

1  Shoveler,   3  shifts @     3 . 00 9 . 00 

Explosives,  powder,  caps  and  fuse 16.90 

Blacksmith  labor,  repairs  and  machine  shop  labor 6.50 

Total  cost  of  five  feet  of  12x8  foot  drift $58.40 

Cost  per  foot 1 1 . 68 

Cost  per  ton  of  rock  excavated 1 1 22 

This  statement  shows  a  decided  reduction  in  cost  per  ton  in  comparison 
with  the  smaller  drift,  and  this  is  as  it  should  be,  for  it  is  well  known  that 
rock  can  be  broken  more  easily  from  a  large  face  than  from  a  small  one. 

Cross  cuts  and  drifts  in  ore  are  from  eighteen  feet  to  twenty-four  feet 
wide  and  ten  feet  to  twelve  feet  high.  These  being  more  or  less  irregular, 
no  estimate  of  cost  can  be  had.  It  is  perhaps  needless  to  say  that  per  ton 
of  rock  excavated  the  cost  is  materially  less  than  in  smaller  drifts. 

As  there  is  very  little  water  in  the  Homestake  Mine,  considering  the 
extent  of  the  openings,  the  main  working  drifts  are  run  on  a  nearly  level 
grade.  No  working  track  has  a  grade  greater  than  one  per  cent,  and  most 
of  the  long  headers  have  a  grade  of  two-tenths  per  cent.  The  drainage  is 
provided  for  by  a  ditch  one  to  three  feet  deep  at  one  side  of  the  drift.  Long 
stringers  of  six-inch  lagging  extend  across  the  ditch  and  are  supported  by 
lagging  at  one  end  while  the  other  end  rests  on  the  ground.  These  stringers 
are  spaced  about  twelve  feet  apart  and  serve  as  ties.  Short  ties  are  used 
between  the  stringers. 

In  some  cases  the  air  pipe  is  laid  on  the  stringers,  directly  over  the 
ditch.  This  method  is  preferable  where  there  are  not  too  many  cross  cuts, 
as  it  does  away  with  a  considerable  expense  in  providing  hangers  for  the  pipe. 
When  the  pipe  is  suspended,  the  electric  wires  may  be  supported  by  wooden 
cross  arms  which  are  fastened  to  the  pipe  by  a  yoke  made  of  round  or  strap 
iron. 

When  required,  tunnel  sets  are  put  in,  but  they  present  no  unusual 
features  to  the ,  average  mining  man. 


Black  Hills  Mining  Meris  Association. 


RAISES. 

Raises  are  made  for  one  of  four  purposes;  namely  .ventilation,  ore  storage 
bins,  transferring  ore  or  waste  from  one  level  to  another  or  to  provide  an 
opening  through  which  waste  may  be  dumped  into  a  finished  stope. 

Permanent  raises  for  ventilation,  ore  bins,  etc.,  are  located  in  the  coun- 
try rock  far  enough  from  the  ledge  to  be  undisturbed  by  mining  operations. 

The  purpose  of  the  waste  raise  is  to  provide  a  storage  for  waste  taken 
from  dead  work  when  not  immediately  needed  in  the  stopes,  and  are  so 
arranged  that  waste  may  be  drawn  out  or  dumped  in  on  any  level.  The 
main  waste  raises  are  connected  with  the  surface  and  the  porphyry  which 
here  forms  a  cap  overlying  the  vertical  formation,  is  drawn  through  them 
and  used  for  filling. 

The  method  of  procedure  is  as  follows:  On  one  or  several  levels,  if 
•convenient,  cross  cuts  are  driven  to  the  point  from  which  it  is  desired  to 
make  the  raise.  Care  must  be  taken  to  have  the  cross  cuts  on  the  different 
levels  alternate  on  each  side  of  a  vertical  plane.  When  the  cross  cut  has 
been  driven  far  enough  beyond  the  position  of  the  raise  to  provide  a  passing 
track  for  empty  cars  the  drift  is  widened,  four  sets  of  regular  stope  timbers 
are  put  in  in  the  form  of  a  square  and  an  ordinary  board  chute  located  in 
one  set.  Above  these  timbers,  the  raise  is  gradually  drawn  in  to  a  6x6  foot 
raise.  From  this  point  the  raise  is  carried  up  in  the  usual  manner.  Sprags 
across  the  raise  about  five  feet  apart  are  used  to  place  the  working  platform 
on  and  serve  as  a  ladder  way.  The  smaller  si/e  machine  drills  are  used  for 
drilling  and  are  raised  and  lowered  by  rope  and  pulley.  The  raise  on  the 
level  below  is  located  about  fifteen  feet  on  either  side  and  is  raised  straight 
to  the  upper  level.  After  connection  has  been  made  an  inclined  by-pass 
is  made  to  connect  with  the  upper  raise  above  the  timbers.  Another  small 
inclined  raise  connects  the  lower  raise  with  the  cross  cut  at  the  top  of  which 
are  located  the  grizzlies.  The  bars  forming  the  grizzly  should  be  spaced 
about  one  foot  in  the  clear  so  that  no  large  rock  can  get  into  the  raise.  The 
successful  operation  of  these  continuous  raises  depends  in  a  great  measure 
upon  the  grizzlies.  The  by-pass  is  closed  by  a  gate  made  of  steel  plate, 
sliding  in  cast  iron  grooves  fastened  to  upright  timbers,  and  operated  by 
rack  and  pinion.  This  gate  is  used  in  the  main  ore  bins  under  the  crushers 
and  is  made  at  the  company's  shop.  It  has  the  advantage  of  being  easily 
operated  and  can  be  operated  gradually  which  prevents  rushes  of  rock. 
Similar  arrangements  are  made  on  the  other  levels.  As  soon  as  one  raise 
is  made  it  can  be  put  into  service  and  the  raises  from  the  lower  levels  finished 
when  needed. 

In  making  an  ore  storage  bin,  the  timber  sets  are  carried  up  six  or  seven 
posts  high.  When  connection  is  made  with  the  level  above  the  timbers  are 
removed  with  the  exception  of  the  sill  floor  in  which  the  chutes  are  located. 
The  by-pass  and  small  raise  to  the  grizzlies  are  located  as  in  the  waste  raise. 

Ingersoll  A-32  machines  are  usually  used  in  making  raises.  One  miner 
and  helper  will  make  a  6x6  foot  raise  100  feet  high  in  ordinary  ground  in 
sixty  shifts,  provided  they  are  not  required  to  car  the  rock. 


Black  Hills  Mining  Men's  Association.  25 

Blasts  are  fired  by  ordinary  caps  and  fuse.  Forty  per  cent,  dynamite 
is  used  as  elsewhere  in  the  mine.  The  manner  of  placing  the  holes  is  similar 
to  that  used  in  small  drifts. 

When  a  stope  has  been  worked  nine  or  ten  floors  high,  raises  are  put  up 
in  convenient  places  to  the  level  above  through  which  the  filling  is  dumped. 
These  raises  are  all  in  ore  and  consequently  pay  their  own  way. 

When  a  raise  is  to  be  made  near  the  face  of  a  long  tunnel  where  the  air 
is  bad  some  artificial  means  of  ventilation  must  be  provided.  A  device  which 
I  believe  originated  with  one  of  the  assistant  foremen  has  proven  very  suc- 
cessful. A  six  or  eight  inch  light  iron  pipe  is  laid  from  the  entrance  of  the 
drift  to  the  foot  of  the  raise.  Near  the  entrance  a  small  one-half  inch  pipe 
is  tapped  into  the  main  air  pipe  and  brought  down  to  and  into  the  large  pipe 
with  the  end  which  projects  into  the  pipe  turned  out.  It  has  been  found 
that  a  very  small  amount  of  air  having  a  pressure  of  from  seventy-five  to 
eighty  pounds  will  effectually  clear  the  raise  in  a  few  minutes.  This  device 
is  used  also  in  running  long  drifts.  An  exhaust  fan  would  possibhr  be  a  more 
economical  machine  so  far  as  power  is  concerned  but  the  first  cost  would  be 
greater  and  the  air  is  used  only  when  the  machine  drill  is  not  in  service. 

STOPING. 

During  the  year  from  June,  1902,  to  June,  1903,  1,279,000  tons  of  ore 
were  milled  by  the  Homestake  Mining  Co.  Approximately  eighty  per  cent, 
of  this  was  mined  on  the  different  levels  from  the  100  foot  to  the  1,100  foot. 
The  remainder  came  from  open  cuts  and  from  "draw  raises"  by  means  of 
which,  as  will  be  explained  later,  the  crushed  ore  left  in  the  roof  of  old  stopes 
is  drawn  out. 

OPEN  CUTS. 

The  ore  obtained  from  the  open  cuts  is  broken  down  from  the  sides  into 
openings  that  connect  with  the  regular  levels  of  the  mine.  These  openings 
or  raises  are  provided  with  chutes  on  the  different  levels  from  which  the 
cars  are  loaded.  The  loaded  cars  are  made  up  into  trains  of  from  four  to 
eight  cars,  according  to  the  grade  of  track  and  hauled  to  the  shaft  by  horses. 

The  ore  taken  from  open  cuts  is  mined  very  cheaply.  Two  miners 
whose  wages  are  $3.50  per  day  will  break,  on  the  average,  200  tons  in  one 
shift.  Two  men  are  employed  at  the  chutes,  one  to  break  the  rock  at  the 
grizzlies  and  one  to  load  the  car.  The  grizzlies  are  located  two  or  three 
floors  above  the  chute.  If  the  haul  is  long  two  horses  with  two  drivers  are 
required  to  haul  the  ore  to  the  shaft.  The  cost  per  ton  of  mining  and  de- 
livering to  the  shaft  is  as  follows: 

2  Miners .  .  .  @  $3 . 50 $7 . 00 

1  Grizzly  man @     3 . 50 3 . 50 

1  Chute  Drawer @     3 . 00 3 . 00 

2  Drivers @     3 . 00 6 . 00 

2  Horses @        .90 1 . 80 

Blacksmith  labor 50 

Explosives,  .026  per  ton 5 . 20 

Total $27 .00 

Cost  per  ton 13£ 


Black  Hills  Mining  Men's  Association. 


Ore  and  waste  is  blasted  down  together  and  the  waste  is  sorted  at  the 
chute  and  used  for  filling. 

In  one  of  the  open  cuts,  now  being  worked,  the  process  of  mining  is 
much  like  the  work  of  making  a  very  deep  thorough  cut  through  a  hill  some 
300  feet  high.  Tracks  are  laid  from  the  crushers  to  one  end  of  the  cut  and 
the  rock  is  blasted  down,  loaded  into  cars  and  trammed  directly  to  the 
crushers. 

ROBBING  OLD  WORKINGS. 

The  pillars  and  backs  of  old  stopes  which  were  left  in  place  in  the  older 
workings  of  the  mine  are  now  being  removed  by  a  system  of  "draw  raises." 
A  description  of  the  method  of  attack  may  be  of  interest  to  many  who  are 
face  to  face  with  the  problem  of  robbing  old  workings  in  vertical  forma- 
tions. 

It  is  very  important  to  know  the  exact  location  of  these  pillars  and 
roofs  before  starting  this  system.  If  the  maps  and  stope  records  have  been 
faithfully  kept  this  becomes  an  easy  matter;  otherwise  the  memory  of  some 
old  employe  must  be  depended  upon  to  give  the  necessary  information. 

Having  located  the  ore,  a  "nine  post  raise"  which  consists  of  four 
regular  stope  sets  arranged  in  a  square,  is  put  up  either  on  the  foot  wall  or 
on  the  hanging  wall  side;  preferably  the  foot  wall.  This  raise  is  carried 
up  a  sufficient  height  to  reach  the  ore  above  the  waste  filling.  Grizzlies  are 
put  in  on  the  floor  next  to  the  top  and  the  sides  of  the  raise  are  carefully 
lagged  to  protect  the  men.  The  run  of  ore  is  then  started  by  a  blast  or  by 
barring.  A  man  stationed  at  the  grizzly  breaks  the  rock  so  that  it  will  pass 
through  into  the  chute  which  is  located  on  the  sill  floor. 

The  timber  required  to  make  a  nine  post  raise  four  floors  high,  is  thirty- 
six  posts,  twenty-four  caps,  twenty-four  ties,  about  150  lagging,  four  stope 
ladders  and  one  ordinary  board  chute.  The  grizzlies  are  made  by  placing 
two  or  three  twelve  inch  timbers,  spaced  twelve  inches  apart,  over  one  set 
and  protecting  these  by  pieces  of  sheet  iron  curved  to  fit.  The  posts  on  the 
top  floor  may  be  protected  in  a  similar  manner,  from  the  blasts  and  from 
running  rock. 

Sixteen  thousand  tons  of  ore  were  taken  from  one  raise  in  six  months ; 
and  this  was  done  in  a  place  where  vain  attempts  had  been  made  to  reach 
the  ore  by  carrying  up  timbered  stopes  through  the  old  fill. 

Should  the  ore  be  too  solid  to  run,  the  raise  will  serve  as  a  manway 
to  a  timbered  stope  started  on  top  of  the  fill. 

Whenever  a  run  of  waste  is  encountered  it  is  drawn  down  and  used  for 
filling  in  other  parts  of  the  mine  and  the  ore  from  upper  levels  will  follow 
the  waste  down. 

TERRA  CAVING  SYSTEM. 

Stoping  without  timbers  was  carried  on  in  the  Deadwood-Terra  Mine 
which  is  now  a  part  of  the  consolidated  Homestake,  for  a  number  of  years 
prior  to  the  time  when  the  Homestake  assumed  control. 

A  cross  cut  from  the  shaft  cuts  the  ledge  which  was  opened  from  wall 
to  wall  throughout  the  entire  length.  All  the  ore  was  removed  from  the 


Black  Hills  Mining  Men's  Association.  27 

sill  floor  excavation.  As  soon  as  the  ledge  was  sufficiently  developed  a 
drift  was  driven  in  the  footwall  approximately  parallel  and  about  twenty 
feet  from  the  ore,  and  openings  made  from  the  drift  into  the  ore  chamber 
at  convenient  intervals.  The  ore  was  then  broken  down  and  the  surplus 
removed  through  these  openings.  As  the  miners  used  the  broken  ore  as  a 
staging  to  work  on,  only  about  forty  per  cent,  of  the  ore  could  be  removed 
until  the  stope  was  finished. 

The  stopes  worked  by  this  method  are  from  thirty  to  fifty  feet  wide  and 
the  dip  of  the  ledge  is  seventy-five  degrees. 

Stoping  may  be  carried  on  on  several  levels  at  the  same  time,  provided 
sufficient  back  is  left  in  between  levels.  When  the  level  above  is  finished 
this  back  may  be  caved  and  all  the  rock  removed  on  the  level  below. 

No  timber  is  required  other  than  a  few  lagging  for  staging,  but  the 
method  is  not  applicable  to  wide  ledges. 

SQUARE  SET  TIMBERING. 

Until  within  the  last  two  years  all  stopes  in  the  Homestake  and  High- 
land Mines  were  timbered  by  the  square  set  method.  An  enormous  amount 
of  timber  was  required  to  timber  the  excavations  and  the  work  of  handling 
the  timber  through  the  shafts  made  it  difficult  to  hoist  sufficient  ore  to  supply 
900  stamps. 

No  unusual  features  are  introduced  in  this  method  of  timbering  so  that 
no  detailed  description  will  be  given.  The  sets  are  six  feet  square,  sill  floor 
sets  are  nine  feet  high  and  all  upper  floor  sets  are  eight  feet,  five  and  one-half 
inches.  A  sill  floor  set  contains  324  cubic  feet  or  about  thirty-two  tons, 
and  an  upper  floor  set  304.5  cubic  feet  or  thirty  tons. 

All  stope  timbers  are  shipped  in  convenient  lengths  to  the  company's 
saw  mill  which  is  located  at  the  Golden  Prospect  shaft.  Here  they  are 
sawed  and  framed  as  needed.  Most  of  the  timber  used  is  native,  although 
some  Oregon  timber  is  used  for  caps  and  ties. 

With  labor  at  $3.00  per  day,  it  has  been  found  that  the  framing  of  what 
is  termed  a  set  of  timber  (a  post,  a  cap  and  a  tie),  costs  sixty  cents  and  the 
cost  for  sawing  lagging  is  five  cents  per  running  foot. 

Two  timbermen  whose  wages  are  $3.50  and  $3.00,  working  one  shift, 
will  stand  timbers,  build  chutes  and  do  all  necessary  repairing  in  a  stope 
which  furnishes  100  tons  of  ore  in  twenty-four  hours.  This  makes  the  cost 
of  labor  for  standing  the  timbers  six  and  one-half  cents  per  ton. 

All  chutes  are  the  ordinary  board  type,  with  bottoms  made  of  lagging 
and  sides  of  two  inch  plank.  The  rock  is  held  back  by  two  boards,  one 
above  but  not  directly  over  the  other. 

On  the  upper  levels  of  the  mine  where  the  ledge  was  broken  and  com- 
paratively narrow,  the  sill  floor  excavation  was  made  from  wall  to  wall  and 
sometimes  for  the  entire  length.  The  sill  floor  timbers  were  then  put  in 
and  the  stopes  worked  where  convenient.  When  the  ledge  began  to  widen 
this  method  proved  disastrous  and  thousands  of  feet  of  lumber  were  used 
to  make  bulkheads  in  a  vain  endeavor  to  keep  .the  stopes  open. 


28  Black  Hills  Mining  Men's  Association. 

A  new  method  was  inaugurated  on  the  600  foot  level  under  the  super- 
vision of  Mr.  W.  S.  O'Brien,  mine  foreman,  which  is  being  used  on  all  new 
levels.  The  plan  is  as  follows:  A  cross  cut  is  driven  through  the  ledge 
from  the  central  shaft  which  is  called  the  main  cross  cut.  The  ore  body 
is  then  developed  by  driving  a  twenty-four  foot  drift  along  the  foot  wall. 
From  this  drift  rooms  sixty  feet  wide  are  opened  across  the  ledge  with  sixty- 
foot  pillars  between  each  stope.  Beginning  with  the  main  cross  cut  a  pillar 
is  left  on  each  side,  then  a  sixty  foot  room,  a  sixty  foot  pillar  and  so  on  to 
the  end  of  the  ore  body.  These  rooms  and  pillars  are  numbered  north  and 
south  of  the  main  cross  cut.  No.  3  Stope  North  would  be  the  third  stope 
north  of  the  cross  cut  and  No.  4  Stope  South,  the  fourth  stope  south  of  the 
cross  cut. 

Some  difficulty  was  experienced  in  keeping  the  sides  of  the  rooms 
straight  while  the  sill  floor  was  being  opened.  To  overcome  this,  sills  were 
laid  in  the  foot  wall  drift  to  lines  given  by  the  surveyor  and  the  miners  took 
their  lines  from  these.  Each  stope  contains  eleven  lines  of  sills.  When  the 
system  once  became  established  no  difficulty  was  experienced  in  keeping 
the  room  of  uniform  width  and  the  sides  comparatively  straight. 

When  a  stope  has  been  worked  and  filled  the  pillar  may  be  attacked 
and  by  lacing  the  sides  next  the  fill  all  the  pillar  may  be  removed. 

HOMESTAKE  SYSTEM. 

However  satisfactory  this  method  of  blocking  out  the  ore  body  may 
be  it  did  not  solve  the  timber  problem.  After  much  deliberation  and  dis- 
cussion it  was  decided  to  try  stoping  in  these  rooms  without  timbers.  Again 
the  practical  ideas  of  the  mine  foreman  and  his  assistants  worked  out  a 
system  which  seems  to  be  well  adapted  to  the  conditions  existing  in  the 
Homestake  Mine  and  which  for  the  sake  of  convenience  has  been  called  the 
"Homestake  System  of  Stoping." 

The  level  is  opened  by  the  room  or  block  method  and  sills  are  laid 
in  the  rooms  the  same  as  for  timbered  stopes.  When  the  sills  are  in,  three 
lines  of  track  are  laid  running  lengthwise  of  the  stope  but  crossing  the  ledge 
with  as  many  cross  tracks  connecting  them  as  are  necessary.  The  sill  floor 
posts  are  put  up  and  lagging  placed  over  the  top,  the  tracks  are  protected 
by  double  lagging  on  top  and  the  rock  is  prevented  from  running  in  at  the 
sides  onto  the  tracks  by  lagging  or  slabs  spiked  to  the  posts. 

As  soon  as  the  timber  is  in  position  the  mining  operation  begins.  The 
ore  is  broken  down  and  allowed  to  fall  through  the  lagging  entirely  filling 
the  sill  floor  sets,  with  the  exception  of  the  carways.  The  lagging,  which 
serves  merely  as  a  staging,  is  removed  as  fast  as  the  sets  are  filled  with 
broken  ore.  No  rock  is  removed  from  the  stope  until  this  filling  is  finished. 
When  the  next  cut  or  breast  is  carried  across  the  stope  some  ore  must  be 
removed  to  make  room  for  the  miner. 

In  the  large  stopes  two  D-24  Ingersoll  machines  are  employed  with 
from  one  to  two  "baby"  machines  which  are  used  to  drill  blockholes  in  the 
large  boulders. 


30  Black  Hills  Mining  Meris  Association. 

Somewhat  of  an  innovation  in  machine  drills  for  block  holing  has  been 
introduced.  A  small  pneumatic  hammer,  such  as  is  used  in  shops  for  chip- 
ping and  caulking,  fitted  with  a  rotating  movement  operates  a  small  drill 
bit  about  one  inch  in  diameter.  This  machine  will  drill  holes  from  six 
inches  to  twelve  inches  deep  and  has  so  far  proven  very  successful  in  block 
holing  large  boulders  in  the  open  stopes. 

As  there  are  no  timbers  to  break,  no  limit  is  placed  on  the  miner  as 
to  the  amount  of  rock  he  may  bring  down  at  one  blast.  The  stope  should 
be  finished  as  quickly  as  possible  so  that  the  broken  rock  may  all  be  removed 
if  needed.  Consequently  large  slabs  of  ore  are  blasted  down  and  these  must 
be  broken  up  to  regular  car  size  either  on  top  of  the  pile  or  on  the  sill  floor 
as  it  is  drawn  down  by  the  shovelers. 

On  account  of  the  uneven  size  of  the  rock  chutes  are  not  generally 
used  in  these  stopes  but  the  car  men  shovel  the  ore  into  cars  from  the  level 
of  the  track,  there  being  as  many  places  to  shovel  from  as  there  are  spaces 
between  posts  along  the  track.  However,  where  the  rock  is  soft  and  where 
it  breaks  fine,  chutes  are  used  to  advantage. 

Should  a  large  rock  come  down  which  the  shoveler  cannot  break  with 
a  rock  hammer,  he  moves  his  car  to  another  opening  until  the  "block  holer" 
comes  around. 

Two  or  three  regular  sets  on  each  side  of  the  stope  are  carried  up  as 
fast  as  the  stope  is  worked  in  which  are  placed  the  ladders  and  air  pipes. 
These  open  sets  also  assist  in  ventilating  the  stope. 

When  the  stope  is  worked  up  eighty  or  eighty-five  feet,  raises  are  made 
to  the  level  above  through  which  the  filling  is  to  be  dumped,  and  the  ore 
is  then  drawn  out.  While  the  ore  is  being  drawn  out,  the  walls  and  roof 
are  carefully  watched  and  all  loose  material  is  dressed  down.  No  accident 
of  a  serious  nature  has  occurred  in  one  of  these  stopes  during  the  two  years 
in  which  this  method  has  been  employed  that  could  in  any  way  be  attributed 
to  the  method. 

When  one  end  has  been  emptied  of  ore,  a  section  of  the  sill  floor  is  lagged 
and  the  filling  is  dumped  in  until  it  begins  to  run  over  the  lagging.  In  this 
way  the  filling  follows  the  shovelers  and  the  walls  of  the  stope  are  supported 
at  one  end  by  the  ore  and  at  the  other  by  the  waste. 

When  small  ore  bodies  are  worked  by  this  method,  no  pillars  are  left 
in,  but  when  one  section  is  worked  up  a  sufficient  height,  another  section 
is  started  at  one  end  and  the  ore  is  left  in  until  the  entire  body  is  worked. 

Stoping  without  timber  is  not  confined  to  the  Homestake  Mine,  but 
there  are  certain  features  of  the  method  as  employed  here  peculiar  to  the 
Homestake  and  which  are  considered  necessary  to  suit  our  conditions.  In 
the  Treadwell  Mine  the  sill  floor  is  not  opened  on  the  station  level  but  drifts 
are  run  in  the  ledge  and  raises  put  up  from  these  drifts  to  a  level  some  fifteen 
feet  above. 

No  timber  is  required  except  for  chutes  but  a  back  of  ore  is  left  in 
which  takes  the  place  of  the  sill  floor  timbers  used  in  the  Homestake.  The 
cost  of  the  timber  would,  in  a  great  measure,  be  offset  by  the  cost  of  making 
raises  and  putting  in  chutes.  The  accessibility  of  the  ore  is  another  ad- 


Black  Hills  Mining  Men's  Association. 


31 


vantage  in  favor  of  the  Homestake  method  and  becomes  a  necessity  in  a 
mine  which  furnishes  nearly  4,000  tons  of  ore  every  twenty-four  hours. 

As  only  a  small  per  cent  of  the  ore  can  be  removed  before  the  stope 
is  finished,  there  is  of  necessity  a  large  reserve  always  on  hand,  which  allows 
the  mine  to  lay  off  whenever  desirable.  The  present  broken  ore  reserve  in 
the  mine  is  nearly  one  million  tons. 

Following  is  a  comparative  table  giving  the  cost  of  timber  in  a  stope 
which  has  been  worked  and  timbered  by  square  sets  and  the  same  stope 
if  worked  by  the  "Homestake  Method." 


TIMBERED  STOPE. 


Name  of  Piece 

No.  of 
Pieces 

Lin.  Ft. 
or  Ft.  B.M. 

Cost  of 
Material 

Labor, 
Sawing, 
Framing 

Total 

Sill  Floor  Posts  
Upper  Floor  Posts  
Caps  

421 
2,077 
2  410 

3,650 
16,616 
13  255 

$474.50 
2,160.08 
1  72°.   1  ^ 

$96.83 
477.71 

KHA   in 

$571.33 
2,637.79 

9  99Q  9^ 

Ties  

2*261 

12  435 

1  filfi   tt 

474.  81 

9  OQ1    9.fi 

Sills.  203  long,  382  short 

4537 

266  85 

22  69 

94Q    1^4 

Lagging  .  . 

13020 

75  906 

37QK    on 

070     KO 

41  74  8°. 

Lagging  strips.    . 

2'410 

4  025  B  M 

fi4   89 

on    nn 

Q4   89 

Wedges  

2  352 

784  B  M 

i  q   oq 

H7(\ 

oc    nn 

47  Sill  Floor  Chutes- 
Complete  

007   no 

215  Upper  Floor  Bins- 
Complete  

824    12 

Ladders  .... 

14 

mB  M 

1    QQ 

3    en 

54Q 

Labor  placing  timbers& 
Chutes  

4  74^  00 

Breakage  (10%  of  Lag- 
ging, 5%  posts,  caps 
ties)  

79°.  Q7 

- 

$11,174.74 

$2,057.08 

$18,770.52 

32 


Black  Hills  Mining  Men's  Association. 


STOPE  WORKED  BY  "HOMESTAKE  METHOD." 


Name  of  Piece 

No.  of 
Pieces 

Lin.  Ft. 
or  Ft.  B.  M. 

Cost  of 
Material 

Labor, 

Sawing, 
Framing 

Total 

Sill  Floor  Posts  

421 

3,650 

$474.50 

$96.83 

$571.33 

Caps  

410 

2,250 

293.15 

86.10 

379.25 

Ties  ,  

381 

2,095 

272.35 

80.01 

352.36 

Sills,  long  

203 

2,436 

121.80 

12.18 

133.98 

Sills,  short  

382 

2,101 

105.05 

10.50 

115.55 

Lagging  

1,752 

10,214 

510.70 

51.07 

561.77 

Lagging  to  protect  track 

764 

4,454 

222.70 

22.27 

244.97 

Relief  Lagging  

1,684 

13,472 

673.60 

67.36 

740.96 

Wedges  

200 

66  B.M. 

1.12 

1.00 

2.12 

MANWAYS. 

Upper  Floor  Posts  

96 

768 

99.84 

22.08 

121.92 

Caps                

48 

264 

34.32 

10.08 

44.40 

Ties  

48 

264 

34.32 

10.08 

44.40 

Lagging,  Floors  

96 

560 

28.00 

2.80 

30.80 

Lagging  Sides  

720 

4,197 

209.85 

20.98 

230.83 

Drift  Pins       

1,440 

457  Ibs. 

22.85 

22.85 

Laders  

28 

235  B.M. 

4.00 

7.00 

11.00 

Labor  Standing  Sill 

758  .  16 

$3,108.15 

$500.34 

$4,366.65 

73,000  tons  taken  from  this  stope. 

18,770.52-73,000 $0.257  per  ton  by  former  method. 

4,366.65-73,000.  ..  .$0.060  per  ton  by  Homestake  method. 
$0.257— $0.060 $0.197  saving  per  ton. 


Black  Hills  Mininy  3/^//'.s  Association.  33 


THE  METALLURGY  OF  THE  HOMESTAKE  ORE. 

BY  C.  W.  MERRILL,  B.  S.,  MEMBER  AMER.  INST.  MINING  ENGINEERS,  MEMBER 

INST.  MINING  AND  METALLURGY,  Assoc.  CHEM.  AND  METALLURGICAL 

Soc.,  S.  A.,  LEAD,  SOUTH  DAKOTA. 

[Revised  from  paper.     Read  before  Black  Hills  Mining  Men's  Association, 
February  19,  1903.     Published  by  Permission  of  A.  I.  M.  E.] 

I.     THE  PROPERTY. 

The  Homestake  Mining  Co.  has  acquired  through  consolidation  the 
ground  and  equipment  of  the  Father  De  Smet  Consolidated  Gold-Mining 
Co.,  the  Dead  wood-Terra  Mining  Co.,  the  Caledonia  Gold-Mining  Co.  and 
the  Highland  Mining  Co.,  at  and  near  Lead,  Lawrence  County,  South  Da- 
kota, in  the  northern  portion  of  the  Black  Hills.  The  company  owns  or 
controls  250  claims,  comprising  2,616  acres,  and  covering  about  8,000  feet 
along  the  strike  of  the  lode. 

At  the  surface  there  are  several  veins,  of  which  three  have  united  in 
depth,  where  the  main  vein  ranges  from  300  to  500  feet  in  width.  The 
1,100-foot  level  is  the  lowest  at  present.  The  rock  of  both  walls  is,  so  far  as 
known  at  present,  carbonaceous  slate,  and  the  country  is  penetrated  by  a 
system  of  porphyry  dikes,  and  in  some  places  capped  with  porphyry. 

The  output  of  the  company  up  to  January,  1903.  has  been,  approxi- 
mately, $70,000,000. 

II.     THE  ORE. 

The  oxidized,  open-cut  ore  is  nearly  all  treated  in  the  three  mills  on  the 
northern  part  of  the  property,  which  are  as  follows:  The  Mineral  Point 
(formerly  the  De  Smet),  of  100  stamps,  the  Monroe  (formerly  Caledonia), 
of  100  stamps,  and  the  Pocahontas  (formerly  the  Dead  wood-Terra),  of  160 
stamps.  A  cyanide  plant,  to  treat  the  leachable  portion  of  the  tailings  from 
these  North  End  mills,  has  recently  been  installed  and  put  into  operation 
at  Gayville,  or  Blacktail  as  it  is  now  known. 

The  Homestake  lower-level  ore,  which  comprises  the  greater  part  of 
that  being  milled  at  Lead,  may  be  described  as  a  hornblende,  garnetiferous 
schist  or  slate,  which  has  been  crushed  and  infiltrated  with  free  silica  and 
pyrites,  the  latter  being  about  seven  or  eight  per  cent,  of  the  ore,  and  com- 
prising pyrite,  pyrrhotite  and  traces  only  of  chalcopyrite  and  arsenopyrite.* 

*The  standards  used  in  this  discussion  are  the  U.  S.  gold  dollar;  the 
U.  S.  short  ton  of  2,000  pounds  avoird.,  and  the  value  of  an  ounce  of  fine 
gold,  $20.67.  Percentages  are  given  by  weight,  and  not  by  volume.  Sizings 
are  classed  as  coarse  (that  portion  of  the  sample  which  will  remain  on  a  100- 
mesh  screen;  diameter  of  wire,  0.00433  inch,  size  of  opening,  0.00575  square 
inch) ;  middles  (the  material  finer  than  the  opening  of  the  above  100-mesh 
screen,  and  coarser  than  the  opening  of  the  commercial  200-mesh  screen  as 
given  below) ;  and  fines  (the  material  which  will  pass  such  a  200-mesh  screen; 
diameter  of  wire,  0.00216  inch;  size  of  opening,  0.00312  square  inch).  A 
further  subdivision  of  fines  is  also  mentioned,  which  is  based  upon  the  granu- 
lar, or  angular,  condition  of  one  portion  and  the  flocculent,  or  amorphous, 
condition  of  the  remaining  portion  of  these  fines. 


34  Black  Hillx  Miniutj  Men's  Association. 


III.     MILLING. 

The  ore  receives  its  first  crushing  in  rotary  breakers  at  the  hoists,  and 
this  product  varies  in  size  from  that  of  sea-sand  up  to  rock  having  an  ex- 
treme dimension  of  four  inches.  From  bins  at  the  hoists  at  Lead,  the  broken 
ore  is  trammed  to  the  three  mills,  i.  e.,  the  Homestake  and  Golden  Star,  con- 
taining 200  stamps  each,  and  the  Amicus  (formerly  the  Highland),  in  which 
there  are  140*  heads,  making  a  total  of  540. 

From  the  mill-bins  the  ore  passes  to  the  mortar,  which  is  of  the  now 
celebrated  Homestake  narrow  pattern,  where  it  is  crushed  between  cast- 
iron  shoes  and  dies,  the  weight  of  the  stamp  when  equipped  with  new  iron 
being  900  pounds,  the  drop  ten  and  one-half  inches  and  falling  eighty-eight 
times  per  minute. 

The  screen  is  of  the  steel-needle  slot-type  No.  8,  and  the  bottom  of  the 
screen-opening  averages  ten  inches  above  the  top  of  the  dies. 

The  long  drop,  high  discharge  and  small  area  of  screen  openings  produce 
an  extremely  fine  pulp,  about  eighty  per  cent,  passing  a  100-mesh  screen, 
and  it  is  to  the  writer  a  most  remarkable  fact  that  under  these  conditions 
such  a  high  stamp-duty  is  maintained,  it  being  fully  four  tons  per  stamp  per 
twenty-four  hours. 

This  duty  is  possible  only  because:  first,  of  the  very  favorable  nature 
of  the  ore,  the  slate  and  pyrite  crushing  readily  and  the  quartz  being  an  ex- 
cellent medium  of  attrition;  secondly,  of  the  large  proportion  of  water  used, 
being  from  eight  to  ten  times  the  weight  of  ore  crushed;  and,  thirdly,  of  the 
narrow  mortar,  which  is  only  twelve  inches  wide  at  the  lip. 

This  very  fine  and  thin  pulp  is  in  the  most  excellent  condition  for  amal- 
gamating, which  process  is  conducted  both  inside  tne  mortar  and  outside,  on 
four  full-size  plates  in  series  (each  54xl44x£  inch;  to  each  mortar.  The  first 
of  these  is  a  copper-plate,  and  the  other  three  are  silver-plated  copper,  the 
weight  of  plating  being  two  Ounces  per  square  foot,  and  all  silver-plating 
being  done  at  the  works.  The  addition  of  the  three  silver-plates  to  each 
stamp-battery  by  Mr.  Grier  has  proved  one  of  the  most  valuable  steps  in  the 
treatment  of  this  ore,  and  has  brought  about  an  additional  profit  amounting 
to,  approximately,  $250,000  during  the  year  1902,  over  and  above  what 
would  have  been  realized  from  amalgamation  had  the  outside  plate-surface 
been  only  that  of  the  one  copper-plate — which,  by  the  way,  is  considered 
ample  in  many  of  the  large  modern  plants  of  the  day. 

In  connection  with  amalgamation,  the  practice  at  the  Homestake  con- 
forms, as  far  as  conditions  will  permit,  to  the  theory  that  the  maximum 
results  are  obtained  when  the  temperature  of  the  water  used  in  the  bat- 
teries is  low  enough  to  exert  the  minimum  influence  on  the  minerals  of  the 
ore;  and  it  is  contended  that  the  plate-yield  proves  the  correctness  of  this 
theory. 

It  would  be  interesting  to  investigate  the  question  of  amalgamation 
and  finer  crushing  in  other  gold-producing  sections,  particularly  in  South 

*This  has  now  (Aug.  15th,  1904,)  been  increased  to  240  stamps. 


36  Black  H-illx  Mining  Men's  Association. 


Africa,  where  the  yield  from  this  source  is  reported  to  be  from  fifty-five  to 
sixty  per  cent.,  as  compared  with  seventy  to  seventy-five  per  cent,  at  the 
Homestake.  Perhaps  finer  crushing  would  not  only  greatly  increase  their, 
amalgam  yield,  but  also  reduce  the  values  lost  in  their  cyanide-residues. 
This  seems  the  more  likely  for  that  country,  because  their  slimes  have  been 
proved  to  have  value  sufficient  for  secondary  treatment,  whereas  this  has 
not  yet  been  proved  at  the  Homestake,  where  the  advisability  of  sliming 
such  a  large  proportion  of  the  ore  has  been  a  debatable  point,  because  the 
slimes  here  contain  only  $0.85  to  $1.10  in  A^alue  per  ton.  But  of  this  more 
will  be  said  later. 

The  total  cost  of  milling  in  the  200-stamp  mills  at  Lead  is,  approxi- 
mately 40  cents  per  ton. 

CLASSIFICATION. 

We  now  have  a  pulp  containing  eight  or  ten  parts  of  water  to  one  of 
ore;  and  much  of  the  latter  is  so  infinitesimally  fine  as  to  cause  a  visitor, 
who  had  watched  an  attempt  to  filter  the  slimes  on  a  large  scale,  to  say  that, 
for  an  exemplification  of  the  size  of  a  molecule,  he  would  advise  the  study 
of  Homestake  slimes. 

The  tailings  as  they  leave  the  mill  are  sized,  with  the  following  result: 

Coarse  (remaining  on  100-mesh),  twenty-two  per  cent. 

Middles  (between  100  and  200-mesh),  eighteen  per  cent. 

Fines  (passing  a  200-mesh  screen),  sixty  per  cent. 

That  is,  sixty  per  cent,  of  the  particles  issuing  from  the  mortar  have 
less  than  0.00001  square  inch  of  cross-section. 

When  the  erection  of  the  cyanide-plant  had  been  determined  upon,  the 
question  of  a  tailings-wheel  to  elevate  the  pulp  and  permit  the  location  of  the 
plant  nearer  the  mills  being  under  discussion,  it  was  calculated  that  to  ele- 
vate the  tailings  at  a  cost  of  about  2  cents  per  ton  would  cost  the  company, 
approximately,  $140,000,  on  .the  proportion  of  the  material  then  blocked 
out  in  the  mine  which  would  be  available  for  leaching.  In  other  words, 
for  every  cent  per  ton  which  could  be  saved  in  the  secondary  treatment  of 
the  leachable  material,  the  company  would  profit  ultimately  to  the  extent 
of  at  least  $70,000.  Consequently,  the  plant  was  located,  as  shown  in  Fig. 
1,  about  a  quarter  of  a  mile  below  the  Lead  mills;  and  the  problems  of 
transportation  and  of  such  classification  as  would  permit  the  pumping-plant 
to  return  its  former  percentage  of  water  to  the  mills,  presented  themselves. 
Another  set  of  16  settling  cones  10  feet  in  diameter  has  recently  been  in- 
stalled. The  latter  has  been  met  by  the  installation  of  the  upper  cone- 
house,  where  twelve  gravity-settling  cones,  seven  feet  in  diameter  and  with 
fifty  degree  sides,  throw  off  about  half  the  water  and,  perhaps,  one-fifth  the 
solid  matter,  which  latter  is  the  very  finest  slime,  of  the  following  sizing, 
during  1902:  Coarse,  0;  Middles,  1.76;  Fines,  98.24  per  cent.  The  thickened 
slimes  are,  subsequently,  settled  out  of  this  pulp,  and  a  part  of  the  water 
is  returned  to  the  mills. 

From  the  bottom  of  the  cones  is  drawn  the  thickened  pulp,  containing 
all  of  the  leachable  material  and  some  of  the  slimes.  This  portion  is  trans- 
ported by  means  of  a  twelve  inch  cast-iron  flanged  pipe  on  a  minimum  grade 
of  2.5  per  cent.,  and  with  as  few  turns  as  possible,  to  the  cyanide  plant. 


38  Black  Hills  Mining  Men's  Association. 

The  second  step  in  the  classification  is  carried  out  in  the  plant  proper 
by  means  of  six  more  gravity-settling  cones,  the  overflow  from  which,  of 
a  like  composition  to  that  of  the  first  twelve  cones,  is  conducted  to  a  collect- 
ing-tank, whence  it  is  drawn  for  the  purpose  of  sluicing  out  the  leachable 
material  after  its  treatment  has  been  completed.  The  average  sizing  of 
this  second  settling-cone  overflow  for  1902  was:  Coarse,  0;  Middles,  1.38; 
Fines,  98.62  per  cent. 

The  under-flow  from  the  second  set  of  gravity-settling  cones,  which  is 
now  quite  thick,  passes  to  twenty-four  (this  number  has  since  been  increased 
to  36)  sizing  or  hydraulic  classifying-cones,  which  carry  a  device  for  dis- 
charging the  sand  and  introducing  the  water,  patented  by  the  writer.  By 
its  means  the  admission  of  water  does  not  result  in  currents  of  varying 
velocity,  which  latter  always  interferes  with  uniform  separation  of  slimes 
from  granular  material.  • 

These  sizing-cones  complete  the  classification,  which  has  been  a  difficult 
problem,  first,  because  of  the  extreme  fineness  of  the  pulp,  and,  secondly, 
because  the  writer  was  determined  to  avoid  double  treatment,  which  entails 
a  largely  increased  installation  and  operating-coat,  but  which  is  necessary, 
unless  a  product  be  obtained  practically  free  from  slime. 

The  slime-overflow  from  hydraulic  classifiers,  had  the  following  sizing 
average  for  1902:  Coarse,  0;  Middles,  1.46;  Fines,  98.54  per  cent.  As  re- 
gards all  slimes  referred  to,  they  will  practically  pass  the  200-mesh  screen, 
the  middles  being  largely  wood-pulp. 

In  fact,  there  is  little  doubt  but  that  the  importance  of  the  most  per- 
fect classification  possible  will  be  recognized  shortly  as  a  vital  consideration 
in  the  cyaniding  of  wet,  crushed  ore;  and  metallurgists  will  not  follow  the  old 
German  practice  of  spitzkasten  and  spitzlutten,  which  are  very  imperfect 
machines  as  compared  with  a  cone-classifier  or  sizer  for  separating  granular 
from  flocculent  material.  The  writer's  judgment  is  that  a  scientific  classi- 
fication-system, by  which  all  the  granular  or  angular  material  may  go  to  the 
leaching  vats,  and  all  the  amorphous  portion  to  the  slime-plant,  will  in  the 
future  be  a  feature  in  designing  a  plant  on  which  the  greatest  care  and  ex- 
perimentation will  be  put,  and  the  highest  grade  of  technical  skill  utilized. 

CYANIDE-TREATMENT. 

By  these  three  steps  in  the  classification  we  have  separated  the  pulp 
into  non-leachable  slimes,  comprising  about  thirty  per  cent,  of  the  ore  crushed, 
and  practically  all  passing  a  200-mesh  screen,  and  a  direct-leachable  product 
amounting  to,  approximately,  seventy  per  cent,  of  the  tailings,  which,  al- 
though very  clean  and  free  from  mud,  is  still  of  a  very  fine  texture, — as  the 
following  sizing  test,  the  average  for  the  year  1902,  will  show: 

Coarse,  remaining  on  100-mesh,  40.5  per  cent. 

Middles,  100  to  200-mesh,  30.8  per  cent. 

Fines,   passing  200-mesh,   28.7  per  cent. 

While  this  fineness  is  notable,  we  find  that,  as  the  proportion  of 
lower-level  ore  increases,  we  can  treat  an  even  finer  product.  A  recent 
charge,  containing  as  high  as  forty  per  cent,  fines,  maintained  our  normal 


40  I  Hack  Hills  Mining  Men's  Association. 


teaching-rate  of  three  to  four  inches  per  hour  throughout  the  treatment. 
This  is  undoubtedly  due  to  the  fact  that  the  fines  from  the  lower-level  rock 
contain  a  greater  proportion  of  angular  or  granular,  and  a  smaller  propor- 
tion of  amorphous,  hydrated  of  flocculent  material. 

The  leachable  pulp,  which  contains  ten  to  twelve  per  cent,  of  pyrite, 
is  now  ready  to  go  to  the  vats;  and  on  the  way  lime  is  added  in  quantities 
varying  from  three  to  five  pounds  per  ton.  At  first  we  tried  adding  this 
lime  in  the  mills,  as  is  done  in  Africa,  but  found  that  the  amalgamation  was 
most  seriously  affected  thereby;  not  only  was  the  plate  completely  coated, 
weeks  being  required  to  get  it  back  in  proper  shape,  but  the  tailings-values 
were  largely  augmented.  This  result  only  emphasizes  the  fact  that  the 
process  must  fit  the  ore,  and  that  attempts  to  make  an  ore  fit  a  process  are 
useless.  This  practice  of  adding  lime  to  the  battery  is,  according  to  the 
writer's  information,  unanimously  pronounced  to  work  the  best  results  in 
Africa,  and  to  reduce  the  values  in  the  slimes  lost  from  amalgamation  to  half 
of  what  they  are  when  no  lime  is  used  in  the  battery.  In  our  case,  however, 
we  have  demonstrated  that  the  best  results  follow  from  crushing  the  lime 
wet  into  a  running  pulp  which  joins  that  from  the  sizing-cones,  whereby 
there  is  less  slacking  and  less  loss  of  flocculent  lime  in  the  vat  overflow,  i.  e., 
in  the  water  which  overflows  the  vat,  the  sand  having  settled  out.  Not 
only  is  it  of  distinct  advantage  to  have  our  lime  go  into  the  tank  in  un- 
slacked  granules,  but  recent  investigations  are  proving  that  the  average 
size  of  these  granules  has  an  important  bearing  on  the  subsequent  cyanide- 
decomposition  and  gold-extraction.  This  seems  to  be  due  to  the  fact  that 
a  low  alkalinity,  but  one  approximately  constant  throughout  the  leaching, 
is  an  important  desideratum  with  the  Homestake  ore,  on  account  of  its 
considerable  content  of  easily-decomposed  sulphides.  We  are  not,  as  yet,  pre- 
pared to  say  what  is  the  very  best  mesh-screen  to  use  on  our  lime  stamp-bat- 
tery, but  at  present  we  are  using  a  wire-screen,  the  opening  of  which  is 
eleven-sixty-fourths  square  inches.  In  this  connection  it  should  be  said  that 
only  the  purest  lime  should  be  used,  the  magnesia  in  the  ordinary  domestic 
limestone  being  objectionable  for  several  reasons. 

The  classified  pulp  and  the  lime  having  comingled,  the  mixture  passes 
to  the  distributor,  which  is  of  the  garden-sprinkler,  or  Butters  and  Mein  type. 
,  There  are  two  distributors,  one  for  each  row  of  vats,  hung  from  a  car- 
riage, which  travels  on  a  track,  and  the  step  of  which  rests  on  the  top  of  the 
center-bottom  discharge-gate  of  each  vat,  when  the  distributor  is  in  operation. 
There  are  fourteen  vats,  each  forty-four  feet  in  diameter,  nine  feet  deep  in- 
side and  holding  610  tons  of  sand.  To  fill  one  of  these  requires  from  eleven 
to  eleven  and  one-half  hours,  which,  with  our  equipment,  permits  of  about 
five  days'  contact  with  solution,  before  it  is  necessary  to  recharge  the  vat. 
After  filling,  the  drain-valve  is  opened,  the  top  leveled,  and  the  stronger 
of  the  two  stock-solutions,  of  a  strength  of  0.14  of  one  per  cent.  KCN,  is  run 
on.  The  contact  with  this  solution,  including  frequent  drainages  for  the 
purpose  of  drawing  in  air,  is  maintained  for  about  three  days.  The  air- 
contact  is  very  important  in  Homestake  ores,  owing  to  the  presence  of 
pyrrhotite  or  subsulphide  of  iron,  which  absorbs  oxygen  with  great  avidity, 


Black  Hills  Mining  Men's  Association.  41 

and  which  would  greatly  retard  the  dissolving  action  of  the  cyanide-solution 
were  not  large  quantities  of  the  essential  oxygen  introduced.  The  effluent 
solution  during  this  period,  having  normally  a  strength  of  0.10  of  one  per 
cent,  of  cyanide,  is  run  to  the  weak  precipitation  tanks,  of  which  there  are 
two,  each  twenty-six  feet  in  diameter  by  nineteen  feet  deep,  and  holding 
300  tons  of  solution. 

After  the  three  days'  contact  with  strong  solution,  the  weak  solution, 
normally  of  a  strength  of  0.10  per  cent.  KCN,  is  brought  into  the  charge, 
and  this  contact  is  maintained  for  the  remaining  two  days.  The  effluent 
solution  from  the  charge  during  this  period  is  run  to  the  strong  precipita- 
tion or  rather  collecting  tanks,  which  are  of  the  same  size  and  number  as 
the  weak  precipitation  tanks. 

Fig.  2  shows  the  interior  arrangement  of  the  works. 

After  contact  with  the  weak  solution  has  been  completed,  wash-water 
is  brought  into  the  charge,  and  the  washing  continued  until  the  effluent 
solution  is  down  to  0.03  or  0.02  of  one  per  cent,  in  KCN  and  from  5  to  7  cents 
per  ton  in  value. 

The  charge  is  now  ready  for  sluicing,  which  operation  is  accomplished 
by.  two  men,  with  three-inch  hose,  in  about  four  hours,  using  the  slime- water 
from  the  overflow  of  the  second  settling-cones.  The  four  side-gates  and  one 
center-gate  afford  ample  facilities  for  the  discharging.  The  last  inch  or  so 
o£  the  sand  is  sluiced  with  clear  water  under  seventy-five  pounds  pressure 
through  one  and  one-half  inch  hose;  and  the  eight  ounce  duck  filter,  under 
which  is  another  of  cocoa-matting,  is  washed  clean.  The  vat  is  then  field 
with  water,  and  is  ready  for  the  next  charging. 

PRECIPITATION. 

As  stated  above,  the  effluent  solution  resulting  from  the  leaching  with 
strong  solution  is  run  to  the  weak  precipitation-tanks,  and  has  a  value  of, 
approximately,  $2.00  per  ton  and  a  strength  of  0.10  per  cent.  KCN.  When 
one  of  these  weak  precipitation-tanks  is  full,  the  stream  is  turned  to  the 
other,  and  the  former  is  then  ready  for  precipitation.  It  contains  300  tons 
of  solution,  which  is  brought  into  agitation  by  means  of  compressed  air, 
and  about  sixty  pounds  of  zinc-powder,  in  the  form  of  an  emulsion,  is  sprayed 
in  during  the  agitation.  The  pump,  which  is  of  the  compound,  duplex, 
outside-packed,  plunger  type,  is  then  -started,  and  the  mixture  pumped 
through  two  larg)  filter  presses,  thirty-six  inches  square,  of  the  flush-plate 
and  distance  frame  pattern,  containing  twenty-four  frames,  each  four  inches 
in  depth. 

While  the  gold,  silver  and  excess  of  zinc  remain  in  the  frame  and  on  the 
cloth,  the  barren  solution  passes  through  the  cloth  and  on  to  the  weak  solu- 
tion storage-tank  below  (of  the  same  size  as  the  sand-vats),  whence  it  passes 
again  to  the  sand  as  weak  solution.  Its  value  has  been  reduced  by  this 
operation  from  $2.00  to  5  or  10  cents  per  ton,  being  a  precipitation  of  95  to 
97.5  per  cent.  The  efficiency  of  this  method  lies  largely  in  the  fact  that  the 
cloths  of  the  presses  are  coated  with  about  one-eighth  inch  of  powdered 
zinc  and  precipitate,  so  that  every  particle  of  solution,  having  to  pass  through 


42  Black  Hills  Mining  Men's  Association. 

the  cloths,  gets  a  molecular  contact  with  the  fine  zinc,  which  is  true  of  no 
other  precipitation-process.  The  presses  are  run  without  opening  for  a 
month,  at  the  end  of  which  the  press  gauges  indicate  about  ten  pounds 
pressure,  notwithstanding  the  fact  that  they  then  contain  about  a  ton  of  pre- 
cipitate worth,  say,  $50,000,  when  they  are  cleaned  up  by  two  men  in  about 
six  hours,  including  the  putting  together  with  new  cloths.  Figures  cover- 
ing the  labor  of  cleaning  up  $50,000  from  zinc  boxes  and  from  electrolytic 
precipitation  would  form  an  interesting  comparison. 

We  will  now  return  to  the  effluent  solution,  resulting  from  the  contact 
of  the  tailings  with  weak  solution  during  the  latter  part  of  the  leaching. 
This  is  run  to  the  strong-solution  collecting  vats.  When  these  are  filled, 
they  are  strengthened  to  0.14  per  cent.  KCN  and  pumped  directly,  without 
precipitation,  to  the  strong-solution  storage  tank,  of  the  same  capacity 
as  the  weak  storage,  whence  it  goes  on  to  the  early  treatment  of  the  charge, 
as  before  mentioned.  Its  value  is  from  30  to  50  cents  per  ton.  It  will  thus 
be  seen  that  the  strong  solution  of  one  day  becomes  the  weak  solution  of  the 
next  day,  and  that  the  values  are  all  accumulated  in  the  weak  precipitation 
tanks.  The  strong  solution  thus  has  an  approximately  constant  value, 
that  is  to  say,  only  one-half  of  the  total  effluent  solution  is  precipitated, 
the  other  half  being  of  a  constant  low  value. 

REFINING  PRECIPITATES. 

As  the  refining  of  cyanide  precipitates  is  of  some  importance,  owing  to 
the  well  recognized  losses  taking  place  in  the  ordinary  methods,  which  are 
from  two  to  six  per  cent.,  a  description  of  the  process  we  use  at  the  Home- 
stake,  in  which  the  loss  is  less  than  0.1  per  cent.,  may  be  of  interest. 

The  precipitate  after  removal  from  the  presses,  is  treated  first  with 
dilute  hydrochloric  acid  in  a  lead-lined  mixing  tank,  equipped  with  a  me- 
chanical agitator,  a  hood,  and  a  powerful  exhaust-fan.  After  agitation,  and 
settling,  the  supernatant  liquid  is  forced  through  a  filter-press  by  air  pressure. 
Sulphuric  acid  is  then  added,  agitation  begun,  and  the  mixture  heated. 
It  is  then  settled,  and  the  supernatant  solution  put  through  the  press,  as  in 
the  case  of  the  hydrochloric  acid.  Wash-water  is  then  added  to  the  mixing 
tank  and  the  whole  mixture  put  into  the  press,  where  it  is  further  washed. 
The  aggregate  value  of  the  acid-liquors  and  wash-water  flowing  from  the 
press  is  less  than  $20.00  from  $50,000  worth  of  precipitate.  A  portion  of 
this  value  is  recovered  from  a  large  settling  tank,  into  which  the  effluent 
solutions  flow,  and  the  remainder  constitutes  the  only  loss  we  have  been  able 
to  find  in  this  process  of  refining. 

The  resultant,  acid-treated  precipitate  is  then  removed  to  a  large  steam 
dryer,  where  a  part  of  the  moisture  is  expelled,  but  never  all,  and  the  pre- 
cipitate mixed  with  litharge,  borax,  silica  and  powdered  coke.  When  thor- 
oughly mixed,  it  is  sprinkled  with  a  solution  of  lead-acetate  and  the  whole 
mass  briquetted  under  a  pressure  of  4,000  to  6,000  pounds  per  square  inch. 
The  zinc  having  been  removed,  and  the  briquettes  having  been  dried,  a 
borax-slag  develops  upon  the  outer  surface  upon  being  charged  to  the  cupel, 
and  they  fuse  quietly,  quickly  and  at  a  low  heat,  without  dust  or  volatili- 


44  Black  Hills  Mining  Men's  Association. 

zation  losses.  The  lead  absorbs  the  values,  sinking  to  the  bottom,  and  the 
slag  is  tapped  off.  All  the  slag  having  been  removed,  the  lead  is  cupelled 
off  as  litharge,  and  the  resultant  metal,  975  to  9S5  fine,  is  ready  to  run  into 
bars.  The  cupel-slag  and  the  cupel-bottom  are  then  put  through  the  blast 
furnace,  the  lead  content  of  the  slag  reduces  to  lead,  which  absorbs  the 
values,  and  is  drawn  from  the  lead  well  in  the  usual  manner.  This  lead  is 
returned  to  the  cupel  at  the  next  clean-up,  the  litharge  from  the  cupellation 
goes  to  the  next  precipitate,  and  the  blast  furnace  slag  is  worth  less  than 
$5.00  per  ton.* 

The  total  cost  of  this  refining  amounts  to  less  than  three-fourths  of  one 
per  cent.;  so  that  the  Homestake  Company  realizes  $20.52  per  ounce  for 
its  cyanide  gold,  less  the  usual  U.  S.  Assay  Office  charges  on  dore  bullion, 
and  the  expressage  to  New  York.  These  charges  amount  to  between  ten 
and  eleven  cents;  and  the  net  realization  per  ounce  of  fine  gold  precipitated 
is  thus  $20.42  in  New  York  exchange.  A  parting-plant  is  now  contem- 
plated, which  will  make  a  further  saving  in  this  connection  and  enable  the 
company  to  turn  out  fine  gold  and  fine  silver. 


TONNAGE,  PERCENTAGE  AND  COSTS. 

TONNAGE. 

The  maximum  monthly  tonnage  of  this  plant — which  is  ascertained 
by  placing  cubic  foot  boxes  in  many  parts  of  various  vats,  determining  the 
dry  weights  per  cubic  foot  of  sand  and  averaging  a  large  number  of  such 
determinations, — was  attained  in  October,  1902,  when  40,236  tons,  or 
1,298  tons  per  day,  wrere  treated.!  This  gives  to  the  Homestake  Company 
the  largest  sand-treatment  cyanide  plant  in  the  world;  the  next  largest 
being,  to  the  best  of  my  knowledge,  that  of  Simmer  &  Jack  in  South  Africa. 

PERCENTAGE. 

As  a  comparison  of  the  various  assay-determinations  and  valuations 
with  the  bullion  produced  is  always  of  interest,  the  following  figures  for  the 
last  half  of  the  year  1902  are  given: 

EXTRACTION. 

The  extraction,  as  shown  by  the  difference  between  charge  and  residue- 
assay  multiplied  by  the  tonnage,  was  $292,579. 

PRECIPITATION. 

The  precipitation,  as  shown  by  the  difference  between  assays  of  unpre- 
cipitated  and  precipitated  solutions  multiplied  by  the  solution  tonnage, 
was  $301,233. 

*The  writer  has  applied  for  patents  covering  this  process,  which  was 
first  carried  out  experimentally  during  the  latter  part  of  the  year  1900. 

fSince  this  paper  was  written,  another  step  in  the  classifying  of  the  pulp 
has  been  added,  with  the  result  that  this  plant  is  now  treating  approximately 
1,450  tons  per  twenty  four  hours. 


Black  Hills  Mining  Men's  Association.  45 

GOLD  IN  PRECIPITATES. 

The  amount  of  gold  in  precipitates,  that  is,  the  assay  value  of  the  pre- 
cipitate sampled  upon  removal  from  the  presses,  was  $302,895;  the  gold 
value  of  bullion  shipped,  $307,635,  and  the  silver  value,  $2,874. 

The  average  percentage  recovered  in  bullion  by  the  treatment  for  these 
six  months  is  74.7  per  cent. 

This  is  not  as  high  a  percentage  of  bullion  as  should  be  recovered  from 
a  porous  or  oxidized  ore,  or  one  in  which  the  values  are  along  cleavage- 
planes;  but,  in  view  of  the  facts  that  such  a  high  percentage  is  recovered 
by  amalgamation,  that  the  values  are  very  finely  disseminated  in  the  Home- 
stake  ore,  and  that  the  tailings  are  very  low-grade,  we  feel,  and  all  our  tests 
so  far  have  verified  our  conclusions,  that  it  is  the  economic  percentage, 
yielding  the  maximum  net  profit. 

Many  tests  and  experimental  runs  of  the  plant,  looking  toward  a  greater 
net.  yield,  have  been  made,  covering  longer  treatment,  stronger  and  weaker 
solutions,  extra  oxidation  with  sodium  and  barium  dioxide,  and  other  similar 
reagents,  varying  alkalinities  and  alkaline  reagents,  etc.  The  question  of 
separate  treatment  of  concentrates  and  coarse  sands  has  also  been  investi- 
gated, all  with  negative  results.  The  conclusion  of  the  writer  in  regard 
to  this  latter  point  is  that,  even  if  a  higher  net  yield  could  be  realized  by 
separate  treatment,  which  is  contrary  to  the  results  of  all  our  tests,  a  much 
greater  proportion  of  the  fines  (passing  200-mesh  screen)  would  have  to  be 
thrown  off  and  wasted,  entailing  a  serious  net  loss. 

COSTS. 

As  to  operating  costs  at  the  Lead  cyanide  plant,  the  following  are  the 
averages  per  ton  for  the  year  1902,  during  which  the  average  value  of  the 
material  treated  was  $1.65  per  ton: 

Classification — Labor  and  Supplies $0.017 

Treatment : 

Cyanide $0 . 152 

Labor 0.030 

Lime 0.022 

Supplies 0 . 005  * 

$0 .209  0 . 209 

Precipitation — Labor  and  Supplies 0.026 

Power — Labor  and  Supplies 0.051 

Water 0.026 

Assaying — Labor  and  Supplies.  .  .  .  : 0.013 

Refining — Labor  and  Supplies 0.006 

Miscellaneous 0 . 005 

Total $0.353 

As  compared  with  the  above,  the  lowest  costs  I  have  seen  authorita- 
tively stated  for  other  plants  are  as  follows: 

City  and  Surbuban,  South  Africa $0.55 

Geldenhuis  Estate,  South  Africa. 0.605 

Geldenhuis  Deep,  South  Africa 0.62 

Robinson,  South  Africa 0.62 

Worcester,  South  Africa.  .  0.72 


46  Black  Hills  Mining  Men's  Association. 


The  African  costs  refer,  of  course,  to  operations  before  the  late  war 
between  England  and  the  South  African  Republic;  but  they  are  the  only 
figures  available  to  me,  and  I  do  not  think  they  have  been  reduced  mater- 
ially since. 

As  regards  the  Homestake  slimes,  which  are  not  at  present  being  treated, 
their  assay-value  ranges  from  $0.80  to  $1.10  per  ton,  which  is  very  much 
lower  than  that  of  any  slimes  now  being  cyanided  elsewhere,  and  which  does 
not  offer  much  inducement  to  undertake  their  hydrometallurgical  treat- 
ment from  them,  with  a  suitable  plant. 


Black  Hills  Mining  Men's  Association.  47 


THE  CYANIDATION  OF  THE  SILICEOUS  ORES  OF  THE  BLACK 
HILLS  OF  SOUTH  DAKOTA. 

BY  CHARLES  H.  FULTOX,  SOUTH  DAKOTA  SCHOOL  OF  MINES. 
[Read  before  the  Black  Hills  Mining  Men's  Association.] 

The  successful  application  of  the  cyanide  process  to  the  siliceous  ores 
of  the  Black  Hills  contributes  more  than  any  other  one  factor  to  the  present 
prosperity  of  the  district.  During  1903  about  $2,200,000  was  produced 
from  the  siliceous  ores  by  cyanidation.  While  the  cyanide  process  was 
introduced  into  the  Black  Hills  about  1892,  at  the  Rossiter  cyanide  plant, 
by  the  Black  Hills  Gold  and  Silver  Extraction  Company,  the  process  was 
not  actually  demonstrated  a  great  success  until  about  1900.  Since  then  a 
considerable  number  of  large  plants  have  been  erected  which  are  operated 
successfully.  At  present  sixteen  cyanide  plants  are  in  operation  in  the 
Black  Hills.  In  1896  the  Rossiter  plant  treated  6,500  tons  of  oxidized  sili- 
ceous ores  by  cyanidation,  while  the  Golden  Reward  and  Keldonan  Chlori- 
nation  Mills  treated  75,000  tons,  so  that  the  prospects  for  the  cyanide  process 
were  not  very  bright.  At  the  present  time,  however,  no  chlorination  plants 
are  in  operation,  and  during  1903  about  550,000  tons  of  siliceous  ores  were 
treated  by  cyanidation.  The  application  of  the  process  has  made  available 
enormous  low-grade  ore  reserves,  which  range  in  value  between  $3.00  and 
$12.00  per  ton.  Ore  above  $12.00  is  generally  considered  of  smelting  grade, 
at  the  present  time.  The  siliceous  Potsdam  ores  are  locally  divided  into 
two  general  classes:  First,  red  ores  (or  the  oxidized  ores),  and  second,  blue 
ores  (or  unoxidized  ores),  of  which  more  will  be  said  later.  In  general  the 
red  ores  readily  yield  a  fair  extraction  to  the  cyanide  process,  ranging  from 
eighty  to  ninety  per  cent,  in  the  district,  the  blue  ores,  however,  fail  in  gen- 
eral to  yield  more  than  thirty  to  forty  per  cent,  of  the'ir  values  to  the  ordi- 
nary process  as  at  present  applied.  Some  mines  have  large  ore  reserves  of 
this  blue  ore  which  is  below  smelting  grade,  and  it  is  but  a  question  of  time 
for  the  successful  cyanidation  of  the  "blue  ores." 

THE  NATURE  OF  THE  ORES. 

The  ores  known  locally  as  the  "siliceous  ores"  are  siliceous  replacements 
of  the  lower  layers  of  lime  shales  which  rest  on  the  Potsdam  quartzite  forma- 
tion. However,  the  siliceous  ores  of  the  same  general  character  occur  also 
at  higher  horizons  in  the  Cambrian,  also  in  vertical  veins,  known  as  "verti- 
cals" and  also  as  siliceous  replacements  of  limestone  in  the  carboniferous, 
as,  for  instance,  the  "Ragged  Top"  ores. 

The  ores  consist  in  the  main  of  silica  in  the  form  of  quartz,  from  seventy- 
five  to  ninety  per  cent.  This  will  range  lower  in  the  unaltered  or  "blue 
ores,"  than  in  the  oxidized  or  "red  ores."  The  blue  ores  contain  from  six 
to  eight  per  cent,  of  fine  grained  evenly  distributed  pyrite,  on  the  average, 
although  this  will  run  up  to  fifteen  to  twenty  per  cent,  in  some  cases.  In 


48  Black  Hills  Mining  Men's  Association. 

the  "red  ores"  this  pyrite  has  been  altered  to  iron  oxides  which  give  the  ore 
its  characteristic  red  color.  Aside  from  these  constituents  the  ores  contain 
small  percentages  of  lime,  alumina  and  alkalies. 

The  presence  of  tellurium  has  been  detected  in  some  of  the  ores,  point- 
ing to  the  probable  existence  of  tellurides  of  gold  and  silver.  Arsenic  is 
found  in  small  quantities  in  the  ores,  and  antimony  in  the  form  of  stibnite 
in  small  quantities  is  not  infrequent.  Copper  occurs  in  traces  only. 

The  gold  in  the  ores  is  present  in  but  very  small  amounts  in  the  free 
state,  and  that  little  is  so  rusty  as  not  to  be  amalgamable.  The  siliceous 
ores  are  in  general  very  hard,  but  while  the  ores  may  be  dense  in  some  dis- 
tricts in  others  they  are  fairly  open  and  porous,  so  that  from  the  physical 
nature  of  the  ores  two  types  of  mills  have  been  developed.  First,  the 
coarse,  dry  crushing  plants,  and,  second,  the  fine,  wet  crushing  plants. 
There  is  another  type  of  plant,  the  fine,  dry  crushing  plant,  which  method 
is  in  competition  with  the  fine,  wet  crushing  methods. 

A  typical  plant  of  the  first  type  (coarse  dry  crushing)  is  that  of  the 

WASP  No.  2  ON  YELLOW  CREEK,  NEAR  KIRK,  SOUTH  DAKOTA. 

This  mill  was  built  during  the  early  part  of  1900,  beginning  operations 
about  September.  It  has  been  running  continuously  since  then,  and  repre- 
sents a  modern  plant,  although  improvements  have  been  made  recently, 
in  increasing  the  capacity  and  in  the  method  of  filling  the  leaching  vats.  It 
is  a  dry  crushing  mill,  and  has  facilities  for  drying  the  ore.  The  mine  is 
within  250  yards  of  the  mill,  the  ore  being  transported  in  trains  of  four 
cars,  by  mule  haulage.  The  cars  hold  1,500  pounds  of  ore,  are  of  the  end 
dump  type,  and  discharge  into  the  main  storage  bin,  of  small  capacity, 
which  feeds  to  the  crusher  floor. 

Nature  of  the  Ore  Treated. 

The  ore  is  of  the  quartzite  variety  from  the  Potsdam.  In  the  greater 
part  of  the  ore  the  gold  is  carried  seemingly  on  the  cleavage  planes  of  the 
quartzite,  and  is  not  finely  disseminated  as  is  usually  the  case,  although 
the  mine  also  has  some  of  this  latter  class  of  ore.  The  fact  that  the  gold 
is  carried  in  the  cleavage  planes  makes  coarse  crushing  permissible,  mani- 
festly a  great  advantage.  Very  little  pyrite  is  present,  but  some  antimony 
in  the  form  of  stibnite  is  found,  although  only  in  small  quantities,  not  suffi- 
cient to  cause  trouble  in  cyaniding.  The  value  of  the  ore  varies  consider- 
ably, generally  running  between  $4.00  and  $20.00  per  ton,  the  greater  part 
being  nearer  the  first  figure  than  the  last.  The  ore  is  at  times  quite  acid, 
requiring  considerable  lime  to  neutralize  it.  .  > 

The  Crushing  of  the  Ore. 

The  mill  site  is  very  favorably  situated  as  regards  slope,  full  advantage 
being  taken  of  gravity,  there  being  but  one  elevator  in  the  mill.  The  capac- 
ity Ojf  the  mill  as  built,  was  from  fifty  to  sixty  tons  per  day,  but  the  instal- 
lation of  a  new  large  tank  raised  this  to  105  tons  per  day. 


50  Black  Hills  Mining  Men's  Association. 

The  Crushing  and  Screening  Machinery. 

The  grizzley  is  eight  feet  long,  four  feet  wide,  with  one  and  one-half 
inch  spaces.  It  is  inclined  at  forty-five  degrees. 

Coarse  crushing  is  done  in  a  No.  3  Gates  crusher,  breaking  to  a  one  and 
one-fourth  inch  ring.  The  capacity  of  the  old  No.  2  crusher  was  about 
sixty  to  sixty-five  tons  per  twenty-four  hours,  and  it  was  found  necessary 
to' put  in  a  No.  3  Gates  in  order  to  come  up  to  the  increased  tankage  capacity 
when  the  new  tank  was  installed.  It  has  been  found  that  a  No.  2  Gates 
has  a  too  limited  capacity,  even  for  a  sixty  ton  mill,  as  the  wet  ore  rapidly 
decreases  its  capacity.  It  is  also  the  experience  that  the  mouth  openings 
are  rather  too  small  for  the  mine  rock,  so  that  too  much  sledging  has  to  be 
done. 

COARSE  ROLLS  (1  SET). — These  are  Gates  rolls,  twenty-four  inches  in 
diameter  and  fourteen  inch  face,  making  eighty  revolutions  per  minute. 
The  ore  is  fed  to  the  rolls  by  Tulloch  automatic  feeds.  The  rolls  are  not 
housed,  as  the  ore  is  damp  enough  to  avoid  much  dust. 

FINISHING  ROLLS  (1  SET). — These  are  of  the  same  make  as  above  and 
the  same  size,  but  make  100  revolutions  per  minute.  A  Tulloch  feed  also 
supplies  these  rolls. 

STATIONARY  INCLINED  SCREEN. — This  is  seven  feet  long,  built  in  two 
partitions,  each  one  foot  wide,  giving  fourteen  square  feet  of  screening 
surface.  It  is  inclined  at  forty-five  degrees.  It  is  two  mesh  wire  cloth, 
or  four  openings  per  square  inch. 

COMBINED  SHAKING  AND  STATIONARY  INCLINED  SCREEN. — This  is  the 
finishing  screen.  The  first  eight  feet  is  a  shaking  screen  and  the  bal- 
ance, about  eight  feet,  being  stationary.  It  is  two  feet  wide,  giving  a 
screening  surface  of  thirty-two  square  feet.  It  is  two  and  one-half 
mesh.  This  inclined  screen  is  on  the  principle  of  the  Berthelet  separator, 
the  material  passing  through  it  being  considerably  finer  than  the  mesh  would 
indicate.  Practically,  the  product  passing  through  this  screen  is  not  above 
six  mesh.  This  is  the  size  of  the  material  cyanided. 

The  Leaching  Department  of  the  Mill. 

There  are  four  leaching  vats,  sixteen  feet  in  diameter  and  seven  feet 
deep.  The  vats  are  of  Oregon  fir,  two  and  one-half  inch  staves,  bound  by 
seven  five-eighths  inch  iron  hoops.  The  capacity  per  vat  is  fifty-five  tons 
of  crushed  dry  ore.  A  new  wooden  100  ton  vat  has  lately  been  installed. 
The  vats  have  a  central  discharge  gate,  14x14  inches,  discharging  the  tail- 
ings into  launders  underneath  the  tanks.  The  new  vat  is  of  larger  size. 

Below  the  leaching  vats  are  situated  the  two  gold  solution  storage  tanks, 
ten  feet  in  diameter  and  six  feet  deep,  also  of  Oregon  fir,  with  two  and  one- 
half  inch  staves. 

Below  the  gold  solution  storage  tanks  are  placed  the  two  sump  tanks, 
of  the  same  size  and  kind  as  the  above.  These  tanks  were  used  formerly 
for  precipitation  tanks,  employing  zinc  dust  as  a  precipitant.  This,  how- 
ever, has  recentlv  been  discontinued. 


Black  Hilh  Mining  Men's  Association.  51 

The  two  solution  storage  tanks  are  situated  above  the  leaching  vats, 
and  are  ten  feet  in  diameter  and  ten  feet  deep,  with  two  and  one-half  inch 
staves.  The  main  solution  pipe  lines  in  the  mill  are  two  and  one-half  inches 
in  diameter,  each  leaching  vat  being  connected,  as  is  customary,  with  both 
the  strong  and  weak  solution  gold  storage  tanks.  There  is  no  vacuum 
connected  with  the  leaching  vats,  as  the  coarseness  of  the  ore  permits  of 
rapid  leaching  and  good  drainage.  Precipitation  is  carried  on  in  wooden 
barrels  by  means  of  zinc  shavings.  There  are  five  barrels  for  the  strong 
solution  and  six  barrels  for  the  weak  solution,  the  barrels  being  three  feet 
deep  and  two  feet  in  diameter  at  the  middle.  They  are  provided  with  a 
screen  at  the  bottom,  on  which  the  zinc  rests,  and  a  rectangular  compart- 
ment on  one  side,  8x4  inches,  by  which  solution  descends  below  the  screen, 
rising  up  through  the  zinc  as  in  the  ordinary  form  of  precipitation  boxes. 
The  advantages  claimed  for  the  barrels  are:  First,  that  the  round  shape 
tends  to  avoid  channeling,  which  causes  irregular  precipitation,  and,  second, 
that  the  clean-up  is  much  facilitated,  because  the  barrels  can-  be  handled 
individually. 

The  Cyaniding  of  the  Ores. 

The  leaching  vats  are  charged  by  means  of  a  belt  conveyor,  which  takes 
the  ore  from  the  finished  product  bin  and  carries  it  to  the  five  leaching  vats. 
This  belt  conveyor  was  installed  recently,  the  mill  as  originally  designed 
having  the  vats  filled  by  end  dump  cars  running  on  tracks  over  the  vats. 
The  conveyor  is  in  two  parts,  that  is,  there  are  practically  two  conveyors 
placed  at  right  angles  to  each  other.  This  is  necessitated  from  the  fact 
that  the  vats  are  placed  in  a  row  at  right  angles  to  the  discharge  end  of  the 
bin.  The  conveyor  proper  is  a  sixteen  inch  rubber  belt,  the  first 
conveyor  fifty  feet  long  and  the  second,  forty  feet  long.  The  speed  of  the 
belt  is  600  feet  per  minute.  By  these  means  a  vat  is  charged  in  from  two 
to  two  and  one-half  hours,  accomplishing  a  great  saving  in  time  over  the  old 
method  of  charging  by  cars.  The  tailings  are  discharged  from  the  vats  by 
sluicing  with  a  water  pressure  of  sixty  to  sixty-five  pounds  per  square  inch. 
The  time  needed  to  discharge  a  vat  is  two  and  one-half  to  three  hours.  The 
favorable  situation  of  the  mill  gives  unlimited  grade  to  carry  off  the  tailings. 

While  the  vat  is  filling,  and  about  one-half  full,  the  strong  solution  is 
turned  on,  six  pounds  of  Potassium  Cyanide  per  ton  of  solution.  The  amount 
of  strong  solution  run  on  is  about  fifteen  tons,  which  is  allowed  to  stand 
three  to  four  hours  generally,  sometimes  much  longer,  according  to  the 
nature  of  the  ore.  When  the  strong  solution  is  started  draining,  the  weak 
solution  is  run  on  and  is  allowed  to  remain  undisturbed  in  contact  with 
the  ore  for  at  least  one  hour;  then  leaching  is  started,  fresh  weak  solution 
being  continually  added  to  replace  that  which  drains  off,  until  wash  water 
is  applied.  The  weak  solution  contains  two  and  one-half  to  three  pounds 
of  cyanide  per  ton.  The  amount  of  weak  solution  thus  brought  into  con- 
tact with  this  ore  is  from  forty  to  fifty  tons.  When  the  gold  value  of  the 
weak  solution  does  not  run  above  thirty  to  fifty  cents  per  ton,  the  wash  water 
is  applied.  The  amount  of  wash  water  is  about  six  to  nine  tons.  The  total 
time  consumed  is  about  ninety-six  to  one  hundred  hours,  including  the 


52  Black  Hills  Mining  Men's  Association. 

charging  and  discharging  of  the  tanks.  The  total  amount  of  the  solution 
used,  including  the  wash  water,  is  seventy  to  seventy-five  tons  per  vat. 

The  amount  of  lime  used  to  neutralize  the  acidity  of  the  ore  and  give 
the  requisite  protective  alkalinity  to  the  solution  is  six  pounds  per  ton  of  ore. 
This  is  added  unslacked  on  the  cars,  before  the  ore  is  dumped  into  the  first 
bin. 

The  protective  alkalinity  is  afforded  by  two  and  one-half  pounds  of 
lime  per  ton  of  solution. 

The  consumption  of  cyanide  is  0.63  pounds  per  ton  of  ore,  and  the 
actual  extraction  ranges  between  eighty  and  eighty-five  per  cent,  of  the 
values  contained  in  the  ore. 

The  Precipitation  by  Zinc  Thread  and  the  Clean-Up. 

The  precipitation  by  zinc  is  practically  perfect,  but  little  trouble  of  a  in- 
kind  being  experienced;  the  rate  of  flow  of  both  weak  and  strong  solution 
through  the  barrels  is  three  tons  per  hour.  The  tailings  solution  issuing 
from  the  barrels  runs  from  four  to  ten  cents  per  ton. 

The  barrels  are  all  provided  with  a  strap  on  each  side,  so  that  they  can 
easily  be  lifted.  When  ready  for  the  clean-up  the  barrels  are  hoisted  up 
and  dumped  into  one  of  the  gold  solution  storage  tanks  which  has  been 
emptied  for  the  purpose.  The  men  get  right  into  the  tank  and  wash  the 
precipitates,  taking  out  all  the  material  that  will  not  pass  a  ten  mesh  screen. 
This  is  put  back  into  the  barrels.  The  fine  material  in  the  tank  is  then 
pumped  through  a  Johnson  filter  press,  having  2x2  foot  frames,  which  was 
formerly  used  in  the  zinc  dust  precipitation.  The  precipitates  are  thor- 
oughly washed  in  the  press  and  then  partly  dried  by  forcing  air  through 
the  press.  Then  the  precipitates  are  discharged  and  are  ready  for  the  acid 
treatment. 

A  small  Worthington  duplex  pump  operates  the  filter  press  by  water 
pressure.  An  air  pump  can  also  be  connected,  so  as  to  force  air  through 
the  filter  press.  The  precipitates,  after  the  drying,  are  charged  into  the 
acid  tank,  which  is  4x4  feet  in  cross  section  and  five  feet  deep,  lined  with 
heavy  sheet  lead.  It  is  provided  on  the  inside  with  several  coils  of  one-half 
inch  lead  pipe,  carrying  steam  to  heat  the  acid  if  necessary.  The  bottom 
of  the  tank  has  a  slight  slope  toward  the  discharge  opening,  a  one  inch  lead 
pipe  in  the  bottom.  The  acid  tank  is  provided  with  a  close  covered  hood, 
which  can  be  raised  and  lowered,  to  facilitate  charging.  The  precipitates 
are  treated  with  dilute  sulphuric  acid,  of  the  usual  strength,  long  enough 
to  dissolve  the  zinc,  then  allowed  to  settle  and  the  solution  syphoned  off. 
Then  water  is  added  and  the  mixture  is  pumped  back  through  the  filter 
press.  Here  it  is  again  thoroughly  washed  with  water,  then  dried  with  air. 
The  dried  precipitates  are  then  heated  to  a  dull  red  in  sheet-iron  pans,  2x4 
feet  in  size,  in  a  large  iron  muffle,  then  smelted  in  graphite  crucibles  with 
the  following  flux:  Seventy  parts  crude  borax,  thirty-five  parts  soda  and 
twenty  parts  of  sand.  The  consumption  of  zinc  is  0.9  pound  per  ounce 
of  bullion  produced. 


51  Black  Hills  Mining  Men's  Association. 


Methods  of  Sampling  Ore,  Tailings  and  Solutions. 

The  pulp  is  sampled  at  the  finished  product  bin  by  the  following  device: 
The  belt  of  the  conveyor  has  one  hole  on  the  center  line  of  the  belt,  and 
every  time  this  comes  under  the  discharge  spout  of  the  bin  some  of  the  pulp 
shoots  through,  falling  on  the  apex  formed  by  two  slant  boards  coming 
together  under  the  center  line  of  the  belt.  This  divides  the  material  into 
two  samples,  which  are  collected  on  the  floor  or  in  large  boxes.  No  infor- 
mation is  available  as  to  the  accuracy  of  the  sample  thus  obtained. 

SAMPLING  THE  TAILINGS. — The  tailings  are  sampled  by  pipe  sampler. 
four  samples  being  taken  irregularly  distributed  over  tha  surface  of  the 
vat.  After  sluicing  has  commenced  a  face  sample  is  taken  at  the  center  of 
the  vat. 

SAMPLING  THE  SOLUTIONS. — The  solution  pipes  entering  the  gold  solu- 
tion storage  tanks  and  leaving  the  zinc  boxes  are  tapped  by  cork  and  a 
small  rubber  tube.  No  clamp  is  used,  however,  and  the  tube  dips  to  the 
bottom  of  a  five  gallon  stone  jar,  the  overflow  going  back  into  the  tanks 
When  the  gold  solution  tank  has  been  filled,  the  solution  man  dips  to  the 
bottom  of  the  jar  with  a  dipper  and  fills  a  small  bottle,  which  goes  to  the 
assay  office.  The  jar  is  then  emptied  and  placed  for  another  sample. 

The  Power  Plant  of  the  Mill. 

Steam  is  furnished  by  two  Erie  return  tubular  boilers,  seventy-five 
horse  power.  The  engine  is  a  Sioux  Corliss,  12x36  inch  cylinder,  eighty- 
five  revolutions  per  minute,  steam  at  eighty-five  pounds  per  square  inch. 
A  separate  small  upright  engine  furnishes  the  power  for  the  conveyor  and 
for  the  dynamo  for  electric  lighting. 

The  Number  of  Men  Employed  in  the  Mill. 

DAY  SHIFT.  NIGHT  SHIFT. 

1  Crusher  man.  1  Roll  man  (takes  rolls  and 

1  Roll  man.  crusher.) 

1  Engineer.  1  Engineer. 

2  Tank  men.  1  Solution  man. 
1  Solution  man. 

1  Millwright. 

1  Superintendent. 

1  Assayer. 

Total  twelve  men.  Wages  for  engineers  $3.50  per  day;  other  mill 
labor,  $3.00  per  day. 

The  Cost  of  Cyaniding. 

The  cost  of  cyaniding  is  $0.832  per  ton,  in  detail  as  follows: 

Labor $0.411 

Cyanide 188 

Zinc .031 

Repairs 086 

Fuel 116 

Total $0 . 832 


Black  Hills  Mining  Men's  Association.  55 

Other  mills  of  the  type  described  are  those  of  the  Spearfish  and  Dead- 
wood  Standard  Companies,  situated  in  the  Ragged  Top  District.  Wherever 
the  ore  yields  its  values  to  coarse  crushing  this  type  of  plant  is  the  most 
economical  as  regards  cost  of  treatment. 

A  typical  plant  of  the  "wet  crushing  type"  is  that  of  the 

DAKOTA  MINING  AND  MILLING  COMPANY  IN  DEADWOOD. 

This  cyanide  plant  is  situated  in  the  First  Ward  of  Deadwood.  It  was 
constructed  during  the  summer  and  fall  of  1901  and  went  into  commission 
in  October.  The  mill  is  a  wet  fine  crushing  mill,  having  a  capacity  of  100 
tons  in  twenty-four  hours. 

The  Crushing  of  the  Ore. 

The  ore  goes  from  the  bins,  which  are  filled  from  railroad  cars,  to  a 
Gates  No.  4  D  crusher,  passing,  however,  first  over  the  grizzley.  The 
crushed  ore  is  carried  by  elevator  to  the  main  storage  bins,  from  which  it  is 
fed  by  suspended  Challenge  feeds  to  six  five-stamp  batteries.,  T.he  weight 
of  the  stamps  is  900  pounds,  the  crushing  being  done  through  a  twenty  mesh 
woven  wire  screen.  The  mortars  have  a  double  discharge,  and  kistead  of 
being  the  ordinary  lip  mortar  are  provided  with  a  gutter  below  the  screens, 
cast  as  one  piece  with  the  mortar.  These  gutters  take  the  pulp  discharge 
from  the  batteries  and  send  it  to  the  charge  box  of  the  spiral  pump.  A 
heavy  canvas  is  hung  over  the  screen  and  gutter  to  prevent  splashing. 

Four  pounds  of  lime  per  ton  are  added  at  the  battery  to  aid  in  the  sub- 
sequent settling  of  the  slimes,  there  being  but  little  acidity  present.  The 
ore  is  crushed  with  a  0.1  per  cent,  or  two  pounds  ot  cyanide  per  ton  solution, 
known  as  "battery  solution." 

It  has  been  found  necessary  to  close  up  some  of  the  rear  discharges  of 
the  batteries  in  order  to  keep  the  amount  of  battery  solution  down  to  the 
normal  amount. 

The  Separating  of  the  Sands  From  the  Slimes. 

The  pulp  from  the  batteries  is  lifted  by  a  Frenier  sand  pump  (capacity 
6,000  gallons  per  hour)  to  the  launders  feeding  the  separator  boxes.  The 
height  of  lift  is  about  seventeen  feet.  The  sands  are  separated  from  the 
slimes  by  means  of  classifier  cones,  two  in  series.  The  slimes  in  the  over- 
flow go  to  the  slimes  vats,  while  the  sands  are  discharged  at  intervals  into 
the  vats  directly  below  the  cones. 

The  Tank  Capacity  of  the  Mill. 

There  are  eight  leaching  vats,  built  in  four  tiers  of  two  each,  for  the 
double  treatment  of  the  sands.  The  vats  are  of  red  cedar,  twenty  feet  in 
diameter  £nd  five  feet  deep. 

There  are  six  slimes  vats,  built  in  two  rows  of  three  each,  each  three  vats 
comprising  a  unit  for  the  treatment  of  one  lot  of  slimes.  The  vats  are  twenty 


Black  Hills  Mining  Men's  Associa  <,on.  57 


feet  in  diameter  and  twelve  feet  deep,  two  and  one-half  inch  staves,  and 
built  of  red  cedar.  There  are  two  sump  tanks,  sixteen  feet  in  diameter  and 
six  feet  deep;  two  gold  solution  tanks,  one  twenty  feet  in  diameter  and  eight 
feet  deep,  the  other  ten  feet  in  diameter  and  five  feet  deep.  Then  there 
are  two  weak  solution  storage  tanks,  sixteen  feet  in  diameter  and  twelve 
feet  deep,  and  also  a  strong  solution  storage  tank,  twelve  feet  in  diameter 
and  seven  feet  deep.  All  these  tanks  are  of  red  cedar.  There  is  one  tank 
twenty  feet  in  diameter  and  eight  feet  deep  used  as  a  settling  tank  to  settle 
out  sediment  from  the  siphoned  slimes  solution. 

The  Treatment  of  the  Sands. 

The  sand  vats  are  charged  in  about  twenty-four  hours,  by  means  of 
the  cones,  and  the  pulp  is  then  leached  with  a  0.2  per  cent.,  or  four  pound 
cyanide  solution,  followed  by  the  weak  solution  of  two  pounds  per  ton. 
The  tailings  are  discharged  by  sluicing,  the  time  consumed  in  discharging 
being  about  two  hours.  The  total  time  consumed  in  treating  sands,  in- 
cluding charging  and  discharging  vats,  is  five  days.  The  extraction  made 
on  sands  varies  with  the  different  ores  treated,  averaging  about  eighty-three 
to  eighty-four  per  cent. 

The  Treatment  of  the  Slimes. 

The  slimes,  coming  from  the  separator  boxes,  flow  into  one  of  the  two 
lowest  slime  vats.  When  one  of  these  vats  is  filled  (the  filling  being  done 
by  carrying  the  slimes  to  the  bottom  of  the  vat  by  a  wooden  pipe),  the 
siphon  is  started  and  the  solution  siphoned  off,  fresh  slimes  pulp  mean- 
while running  into  the  vat  continually.  This  can  be  done,  as  the  slimes 
settle  very  rapidly  with  most  of  the  ores  treated  at  the  mill.  When  so  much 
slime  has  been  charged  into  the  vat  that  the  siphoned  solution  begins  to  be 
seriously  discolored,  twenty-five  pounds  of  slacked  lime  are  fed  into  the 
launder  taking  the  slimes  overflow  from  the  separator  boxes,  and  when 
this  has  been  carried  into  the  slimes  vat,  the  pulp  is  changed  into  the  lowest 
slime  vat  of  the  second  unit,  where  the  above  operation  is  repeated.  The 
slimes  in  vat  No.  1  are  then  allowed  to  settle  for  one  hour,  when  the  siphon 
is  again  started,  and  now  follows  the  settling  of  the  slimes  down  until  the 
solution  has  been  drained  within  a  few  inches  of  the  settled  slimes.  The 
total  time  of  settling  is  about  ten  hours.  The  settled  slimes  in  this  vat  are 
now  sluiced  out  with  "barren  solution"  to  the  centrifugal  pump,  which  lifts 
the  material  to  the  next  slime  vat  of  the  unit.  When  the  vat  has  been  filled 
the  pulp  is  drawn  off  at  the  bottom  by  the  centrifugal  pump  and  returned 
to  the  vat  over  the  top.  This  circulation  is  carried  on  for  an  hour.  Then 
the  slimes  are  allowed  to  settle,  the  clear  solution  at  the  top  being  siphoned 
off  during  the  settling.  When  the  slimes  have  settled,  fresh  barren  solution 
is  added  and  they  are  circulated  by  the  centrifugal  pump  for  another  hour, 
twenty-five  pounds  more  of  lime  being  added  in  the  course  of  the  pumping. 
The  slimes  are  then  again  allowed  to  settle,  while  the  solution  is  siphoned 
off  as  before.  When  settling  is  complete  the  slimes  are  sluiced  out  with  wash 


58  Black  Hills  Mining  Men's  Association. 

water  to  the  centrifugal  pump,  which  now  raises  the  pulp  to  the  last  slime 
vat  of  the  unit.  Here  the  slimes  are  allowed  to  settle  again  and  the  solu- 
tion siphoned  off.  After  the  solution  has  been  drawn  off  wash  water  is 
added  by  a  nozzle  and  pipe  device  situated  in  the  vat.  This  serves  to  thor- 
oughly wash  and  agitate  the  slimes  for  the  last  time.  The  slimes  are  now 
allowed  to  settle,  while  the  solution  is  drawn  off  by  the  siphon.  Then  the 
slimes  are  sluiced  out  to  waste,  having  passed  through  three  vats.  The 
extraction  made  on  slimes  is  about  eighty-eight  per  cent.,  but  at  present 
only  about  eighty  to  eighty-two  per  cent,  is  saved,  the  balance  passing  out 
in  the  tailings  in  the  retained  moisture.  More  thorough  washing,  with  facil- 
ities for  handling  this  increased  bulk  of  wash  water,  will  undoubtedly  raise 
the  percentage  saved.  The  total  time  consumed  is  about  six  days. 

The  Precipitating  Department. 

Precipitation  is  carried  on  in  four  zinc  boxes,  two  for  siphoned  solution 
and  two  for  sands  solution.  There  are  ten  compartment  boxes,  each  com- 
partment having  a  cross  section  of  20x15  inches  and  a  depth  of  about  eighteen 
inches.  Some  extra  precipitating  barrels  are  being  put  in  to  accommodate 
an  increased  amount  of  solution.  The  precipitates  can  be  sluiced  from  the 
boxes  to  the  acid  treatment  tank,  where  they  are  washed  and  treated  with 
dilute  sulphuric  acid  in  the  usual  way,  transferred  to  a  filter  tank,  filtered, 
washed  and  dried,  and  then  smelted.  The  slags  are  treated  at  the  Golden 
Reward  Smelter. 

The  precipitation  in  the  boxes  is  good  for  both  sands  and  slimes  solu- 
tions, the  slimes  solutions  usually  carrying  from  .05  to  .08  per  cent,  free 
cyanide.  Considerable  sediment  sometimes  accumulates  in  the  boxes,  but 
does  not  seem  to  give  any  trouble  in  precipitation. 

The  Nature  of  the  Ore  Treated. 

The  ores  treated  at  the  mill  come  mainly  from  the  vicinity  of  Portland, 
and  are  siliceous  Potsdam  ores,  with  the  values  very  finely  distributed. 
The  mill  also  treats  custom  ores  to  a  considerable  extent.  Recently  some 
siliceous  ores  have  been  treated  which  were  but  slightly  oxidized,  seem- 
ingly with  considerable  success. 

The  Dakota  Mill  is  very  similar,  at  least  in  plan  of  treatment,  to  the 
Mogul  Mill  of  the  Horseshoe  Company  at  Terry,  the  Penobscot  Mill 
at  Garden  City,  the  Columbus  Mill  at  Central  the  Hidden  Fortune  Mill  and 
other  smaller  mills  of  the  district.  The  cost  of  treatment  by  the  method 
described  is  from  $1.25  to  $1.50  per  ton,  depending  on  the  scale  of  opera- 
tions. 

A  typical  plant  of  the  third  type  (fine  dry  crushing)  is  that  of  the 

IMPERIAL  MINING  AND  MILLING  COMPANY  OF  DEADWOOD. 

This  plant  is  located  a  short  distance  from  the  Dakota  plant,  already 

described.  It  is  a  dry  crushing  plant,  with  roasting  facilities  for  the  heavier 

'blue"  ores,  and    has  a    capacity  of  150  tons  per  day,  with  provisions  to 


Black  Hills  Mining  Men's  Association.  59 

increase  to  250  tons  in  time.  The  power  plant  is  sufficient  for  the  latter 
capacity.  The  plan  of  the  mill  follows  the  Colorado  pattern  at  Florence, 
treating  telluride  ores  from  the  Cripple  Creek  district.  It  is  built  entirely 
on  level  ground,  the  crushing,  roasting  and  leaching  departments  being  in 
separate,  but  closely  adjoining  buildings,  the  transference  of  pulp  being 
accomplished  by  elevators  and  belt  conveyors.  The  whole  plant  is  built 
very  substantially  on  solid  concrete  foundations.  The  building's  are  all 
iron  clad. 

The  mill  represents  a  different  type  from  that  usually  to  be  found  in  the 
Black  Hills,  and  as  it  is  to  treat  ores  of  the  same  nature  that  the  Dakota  and 
Portland  mills  are  treating,  in  fact  from  properties  in  close  vicinity  to  the 
mines  of  the  latter  mills,  a  comparison  could  be  made  between  the  two  methods 
of  treatment,  which  would  be  of  considerable  interest,  as  regards  the  relative 
merits  of  fine  dry  and  fine  wet  crushing  with  the  slimes  treatment  of  the  latter 
method.  As  the  mill  is  designed  to  treat  custom  ores,  two  Vezin  samplers, 
placed  in  series,  are  being  installed,  with  the  necessary  sample  crushing 
plant  to  further  reduce  the  sample  cut  out  by  the  samplers. 

The  Crushing  Machinery. 

A  shaking  grizzley,  four  feet  long  by  two  feet  wide,  takes  out  the  fines, 
while  the  coarse  ore  goes  to  a  10x20  Blake  crusher.  The  ore  is  further 
crushed  by  one  set  of  Davies  rolls,  sixteen  inch  face  and  thirty-six  inches 
in  diameter,  with  Latrobe  steel  shells.  The  rolls  make  sixty  revolutions  per 
minute.  The  crushed  ore  then  goes  through  the  Vezin  samplers,  after 
which  the  bulk  of  the  ore  is  dried  in  a  Davies  multi-tubular  dryer  (a  revolving 
cylindrical  drying  furnace),  and  then  goes  to  two  sets  of  finishing  rolls  after 
being  screened  over  an  eight  mesh  inclined  screen.  Each  finishing  roll, 
with  its  following  four  revolving  screens  and  elevators,  is  constructed  as  a 
unit,  so  that  one  set  of  rolls  can  be  run  independently  of  the  other.  The 
advantage  of  this  is  evident  in  case  of  a  breakdown  in  the  crushing  machinery. 
The  finishing  rolls  are  of  the  Davies  type,  thirty-six  inches  in  diameter  and 
sixteen  inch  face,  having  a  speed  of  eighty  revolutions  per  minute.  It  is 
seen  that  the  roughing  rolls  and  finishing  rolls  are  of  the  same  size,  permit- 
ting of  change  of  the  roll  shells,  from  the  finishing  to  the  roughing  rolls,  when 
the  first  become  too  uneven  for  uniform  crushing. 

All  the  rolls  and  screens  are  steel  housed,  and  these  housings  are  con- 
nected by  two  Sturtevant  exhaust  fans,  wnth  two  Prinz  and  Rau  dust  col- 
lectors, consisting  of  a  revolving  spindle,  on  which  are  stretched  collecting 
bags.  The  dust  is  drawn  in  at  the  center  of  the  spindle  and  collected  in  the 
bags,  from  which  in  turn  it  is  discharged,  by  automatically  shaking  the  bags, 
the  collected  dust  being  carried  by  a  conveyor  to  the  pulp  bins  and  mixed 
with  the  pulp.  In  this  way  no  dust  is  accumulated  for  separate  treatment, 
but  what  is  formed  is  treated  with  the  pulp. 

The  pulp  storage  bin  is  divided  into  two  divisions  of  250  tons  each, 
one  for  sulphide  ores  and  one  for  the  oxidized  ores,  these  being  kept  separate 
throughout  their  course  through  the  mill,  the  sulphide  ore  going  from  the 
bins  to  the  roasting  furnace. 


€0  Black  Hills  Mining  Menu  Association. 

The  Roasting  Furnace. 

Th^s  is  a  Holthoff-Wethey  two  hearth  furnace,  the  upper  hearth  being 
the  roasting  hearth,  while  the  lower  one  acts  as  a  cooling  hearth.  The  in- 
side dimensions  of  the  hearth  are  121  feet  length  and  twelve  feet  width.  The 
outside  dimensions  are,  length  131  feet,  width  fourteen  feet.  By  the  time 
the  ore  gets  to  the  lower  end  of  the  cooling  hearth  it  is  cool  enough  to  be 
taken  by  the  elevator  and  raised  to  the  bins.  The  ores  to  be  roasted  are 
light  in  sulphur. 

The  Leaching  Department  of  the  Mill. 

There  are  four  steel  leaching  vats,  thirty-five  feet  in  diameter  and  six 
feet  deep,  the  body  being  of  three-sixteenth  inch  steel  and  the  bottom  of 
one-fourth  inch  steel.  The  vats  hold  200  tons  and  have  five  bottom  dis- 
charge gates,  operated  from  above.  There  are  also  four  smaller  leaching 
vats,  placed  so  as  to  utilize  the  waste  room  left  by  the  large  vats,  due  to 
their  circular  shape.  These  are  ten  feet  in  diameter  and  six  feet  deep,  hold- 
ing sixteen  tons.  There  are  two  gold  solution  storage  tanks,  sixteen  feet 
in  diameter  and  four  feet  deep,  and  two  sump  tanks  twenty  feet  in  diameter 
and  four  feet  deep  and  two  solution  storage  tanks,  twenty  feet  in  diam- 
eter and  four  feet  deep,  all  of  steel,  same  size  of  material  as  the  leach- 
ing vats.  Precipitation  is  carried  on  by  zinc  thread  in  steel  precipitation 
boxes.  The  sulphuric  acid  method  is  used  to  refine  the  precipitates.  The 
leaching  vats  are  connected  with  vacuum  chambers,  to  facilitate  the  final 
washing  of  the  pulp. 

The  Power  Plant. 

There  are  two  Heine  water  tube  boilers,  of  125  horse  power  each,  to  carry 
150  to  200  pounds  of  steam  pressure.  The  engine  is  a  250  horse  power  tan- 
dem compound  Hamilton  Corliss,  non-condensing.  There  is  an  electric 
light  plant  of  250  lights.  The  power  plant  is  large  enough  for  a  250  ton  mill, 
and  it  is  intended  to  eventually  install  two  more  sets  of  finishing  rolls,  with 
their  screens  and  elevators,  and  four  more  thirty-five  foot  leaching  vats. 
The  actual  cyanidation  of  the  crushed  ore  is  very  similar  to  that  described 
for  coarse  dry  crushing. 

(We  add  in  connection  with  Mr.  Fulton's  article  a  description  of  the 
Lundberg,  Dorr  &  Wilson  plant  by  Mr.  A.  D.  Wilson,  as  being  a  new  type 
of  mill  for  the  Black  Hills  and  which  had  not  been  completed  when  Mr. 
Fulton's  article  was  written. — Committee.) 

LUNDBERG,  DORR  &  WILSON  CYANIDE  MILL. 

This  mill,  of  seventy-five  tons  daily  capacity,  situated  upon  the  prop- 
erty formerly  owned  by  the  Buxton  Mining  Co.,  is  held  under  the  private 
ownership  of  John  Lundberg  of  Terry,  S.  D.,  John  V.  N.  Dorr  of  Terry,  S. 
D.,  and  A.  D.  Wilson  of  Deadwood,  S.  D.  This  is  the  first  mill  in  the  Black 
Hills  to  use  electric  power,  to  use  a  modern  type  of  the  Chilian  mill,  to  use 
a  belt  elevator  for  the  elevation  of  pulp,  to  use  the  Moore  Process  for  the 


Black  Hills  Mining  Men's  Association.  61 

finished  treatment  of  slimes,  and  to  use  the  Dorr  Mechanical  Classifier. 
The  ore  first  passes  through  a  No.  4  Gates  crusher,  and  is  elevated  to  a  stor- 
age bin.  From  the  storage  bin  it  is  fed  by  a  shaking  trough  to  a  set  of  coarse 
rolls  which  reduce  it  to  about  three-fourths  inch  size.  As  it  passes  through 
these  rolls  the  solution  of  cyanide  of  potassium  is  added  and  carries  all  the 
material  to  the  Chilian  mill.  This  mill  is  a  six  foot  Monadnock  Mill,  manu- 
factured by  S.  V.  Trent  &  Co.,  of  Salt  Lake  City,  whose  three  ponderous 
rolls,  weighing  6,600  pounds,  revolving  at  a  speed  of  thirty-one  revolutions 
per  minute,  strike  ninety-three  blows  per  minute  upon  any  part  of  the  die. 
From  the  mill  the  ore  and  solution  is  elevated  by  means  of  a  belt  elevator, 
to  the  Dorr  mechanical  classifier,  where  the  sands  and  slimes  are  separated. 
The  sands  are  carried  from  the  classifier  to  the  leaching  tanks,  eighteen  feet 
in  diameter  and  ten  feet  'deep,  where  they  undergo  the  ordinary  process  of 
leaching.  From  the  classifier  .the  slimes  are  carried  to  the  cone  settler. 
This  cone  is  twenty-two  feet  in  diameter  and  fourteen  feet  deep,  with  a 
carefully  leveled  overflow.  The  clear  solution  is  reused  and  the  thickened 
slimes  are  drawn  from  the  bottom  and  delivered  to  the  slime  storage  tank 
where  they  are  given  an  aeration.  From  the  slimes  storage  sank  the  slimes 
are  drawn  off  to  the  first  tank  of  the  Moore  Slimes  Process.  This  tank  has 
hopper  bottoms  and  air  pipes.  From  the  bottoms  of  the  hoppers  the  slimes 
are  drawn  continuously  by  means  of  a  power  diaphragm  pump  and  poured 
back  into  the  top.  This,  with  the  agitation  provided  by  the  air  pipes,  gives 
the  slimes  a  thorough  aeration. 

The  Moore  filter  plates  of  which  there  are  thirty-four  4x6  feet,  attached 
to  one  framework,  affording  a  filtering  surface  of  1,632  square  feet,  are  then 
lowered  into  this  first  tank,  and  the  vacuum  pump  started.  The  solution 
comes  through  these  filters  very  clear  and  is  piped  to  the  zinc  boxes.  The 
slimes  form  a  thick  coat  upon  the  outside  of  the  filter  frames.  When  a 
thickness  of  about  three-fourths  inch  is  attained  the  filters  are  raised  out 
of  the  tank  and  by  means  of  a  traveling  crane  are  moved  over  and  immersed 
in  a  tank  carrying  barren  solution.  The  suction  is  still  continued  and  the 
gold  bearing  solution  replaced  by  the  barren  solution.  The  filters  are  again 
raised  and  immersed  in.  clear  water,  which  replaces  the  barren  solution. 
The  filters  are  again  raised  and  moved  over  the  discharge  hoppers  where  a 
large  volume  of  compressed  air  is  blown  into  them.  This  releases  the  coating 
of  slimes  and  carrying  about  thirty  per  cent,  moisture  it  drops  down  into 
the  discharging  hoppers  from  which  it  is  drawn  into  a  hopper  bottom  car 
and  thrown  out  on  the  dump.  The  length  of  time  occupied  by  the'  above 
cycle  is  three  hours,  and  the  amount  of  slimes  to  a  charge  is  four  and  one- 
half  tons  dry.  The  sands  are  shoveled  from  the  tanks  through  a  central 
discharge  hole  into  a  four  ton  car,  with  side  discharges,  and  thrown  out  on 
the  dump.  The  mill  is  under  the  superintendency  of  John  V.  N.  Dorr. 


Black  Hills  Mining  Men's  Association.  63 

WET  CRUSHING  IN  SOLUTION. 

BY  JOHN  M.  HEXTON. 
[Paper  read  before  the  Black  Hills  Mining  Men's  Association,  April  22,  1903.] 

My  subject  is  "Some  of  the  History  of  Wet  Crushing  in  Cyanide  Solu- 
tion," and  so  you  are  guarded  against  expecting  all  the  history  and  I  can 
excuse  myself  for  all  omissions.  What  I  may  say  purports  to  be  history, 
and  history  is  a  record  of  events  which  should  teach  something  by  showing 
the  steps  of  progress  and  development,  the  details  of  which  are  often  unin- 
teresting and  wearysome  and  I  ask  your  kind  indulgence. 

By  way  of  introduction  I  will  quote  from  "The  Cyanide  Process,  Its 
Practical  Application  and  Economic  Results,"  by  Dr.  A.  Scheidel,  San  Fran- 
cisco, October  1,  1894.  On  page  28,  in  writing  of  the  practice  in  general 
Dr.  Scheidel  says,  "Many  attempts  have  been  made  to  discharge  ore  pulp 
direct  from  the  mortars  into  the  percolating  vats  but  their  successful  treat- 
ment by  cyanide,  when  so  discharged,  has  been  prevented  by  mechanical 
causes  and  in  consequence  of  the  presence  of  slimes  the  results  are  unsatis- 
factory. The  advantages  of  wet  crushing  over  dry  crushing  are  so  obvious 
however,  that  experiments  will  be  continued  and  ultimately  the  draw-backs 
which  now  adhere  to  the  method  will  be  overcome.  Cyanide  of  potassium 
solution  has  been  used,  in  some  instances,  and  in  an  experimental  way,  in 
lieu  of  water  in  the  mortars,  when  wet  crushing  has  been  resorted  to,  but 
does  not  appear  to  be  practiced  anywhere  at  present." 

On  page  48,  speaking  of  the  practice  in  South  Africa,  he  says:  "In 
an  experimental  way,  a  solution  of  cyanide  has  been  used  instead  of  battery 
water;  at  present,  however,  water  is  invariably  used  in  the  mortar  boxes, 
sufficient  success  not  having  attended  the  other  methods.  The  use  of 
cyanide  solution  in  the  mortars  would  be  of  advantage  only  when  the  pulp 
is  directly  .delivered  into  the  percolation  vats;  the  formation  of  slimes  is 
fatal  to  this  method."  On  page  76,  an  extract  from  the  New  Zealand  Gov- 
ernment Report  is  given:  "The  Try  fluke  Co.  tried  to  run  the  tailings 
directly  into  the  tanks  but  they,  like  others,  found  that  the  amount  of  slimes 
in  the  ore  prevented  the  cyanide  solution  from  filtering."  It  will  be  noticed 
that  one  universal  difficulty  was  encountered,  namely,  slimes.  The  word 
slimes  is  the  key  to  a  correct  understanding  of  the  subject  of  wet  crushing 
in  cyanide  solution. 

I  will  quote  now  from  page  67  of  Bulletin  No.  5  of  the  South  Dakota 
School  of  Mines.  I  make  this  quotation  in  order  to  correct  and  not  to  find 
fault.  "The  method  of  working  the  Deadbroke  mill,  treating  the  pulp  from 
the  plates,  led  to  the  direct  crushing  of  the  ores  in  the  battery  with  cyanide 
solution  in  the  Gayville  and  Central  City  mills."  How  such  a  result  could 
have  followed  from  the  method  of  working  the  Deadbroke  mill  it  is  hard  to 
imagine,  for  no  attempt  was  ever  made  at  that  mill  to  treat  the  slimes 
which  were  allowed  to  run  wholly  to  waste,  and  thus  the  slimes  problem  re- 
mained in  the  old  unsolved  condition  as  related  to  saving  any  values  which 


64  Black  Hills  Mining  Men's  Association. 

they  might  contain;  nor  was  direct  filling  attempted  until  after  the  building 
of  the  Dakota  mill  at  Central  City  by  Capt.  Bullock;  nor  was  cyanide  at  any 
time  ever  used  in  the  batteries.  And  in  any  other  way  than  those  any  other 
stamp-mill  could  be  said  to  have  led  to  this  method  of  cyanide  practice. 
The  slimes  problem  being  the  only  serious  difficulty  to  meet  in  wet  crushing 
in  cyanide  solution,  it  might  have  led  to  a  better  understanding  to  have  en- 
titled this  paper  "Some  of  the  History  of  Slimes  Treatment." 

February  19,  1898,  Chas.  Butters,  a  chemist  of  South  Africa,  delivered 
an  address  in  Johannesburg  on  the  treatment  of  slimes  which  gives  the  best 
practice  up  to  that  date. 

The  reading  of  the  address  would  take  an  entire  evening  and  only  a  few 
sentences  can  be  given  here.  After  saying  that  he  had  "been  specially 
employed  on  the  slimes  problem  for  the  past  three  years,"  he  continues, 
"These  researches  have  resulted  in  the  working  out  of  a  practical  method 
which  consists  in  the  coagulation  of  the  slimes  in  battery  water  by  means  of 
lime,  their  concentration  by  spitzkasten  and  final  settlement  in.  continuous 
overflow  vats.  These  settled  slimes  are  now  ready  for  treatment.  Three 
methods  for  dissolving  the  gold  are  at  present  in  use  on  these  fields.  One 
consists  for  pumping  the  fresh  slimes  from  one  tank  to  another  through  a  cen- 
trifugal pump;  the  second,  the  fresh  slimes  are  agitated  in  a  dissolving  vat, 
by  means  of  a  stirring  gear,  for  six  or  eight  hours;  the  third  consists  of  a 
joint  use  of  both  of  these  former  methods.  At  the  Bonanza,  agitation, 
aeration,  with  an  air  compressor  through  a  pipe  placed  near  the  bottom  of 
the  vat,  and  circulation  through  a  centrifugal  pump,  are  all  in  use  at  the 
same  time.  With  decantation  the  washing  of  the  material  takes  place  by 
dilution,  one  wash  does  not  displace  another  wash  but  simply  mixes  with  it. 
Decantation  as  ordinarily  practiced  means  that  a  ton  of  solution  is  thrown 
away  with  every  ton  of  slimes.  To  reduce  this  large  amount  of  solution 
thrown  away  we  have  erected  at  the  central  works  of  the  Rand  Central  Ore 
Reduction  Company,  the  two  largest  vats  in  the  world,  each  being  fifty  feet 
in  diameter  and  sixteen  feet  deep.  It  has  been  found  that  by  filling  these 
gradually  and  allowing  them  to  settle  for  about  a  week,  the  pressure  exerted 
by  the  great  depth  of  settled  slimes  reduce  the  average  moisture  to  about 
forty  per  cent."  Mr.  Butters  closes  his  address  by  saying,  "It  appears  pos- 
sible that  the  aim  of  the  metallurgist  will  soon  be  to  increase  the  percentage 
of  slimflfe  produced  by  the  mill." 

Americans  are  not  generally  much  behind  the  balance  of  the  world 
Mr.  M.  W.  Alderson  writes  of  what  was  being  done  in  Montana  in  the  M.  & 
S.  Press,  "In  the  winter  of  1895-6  laboratory  tests  were  made  in  Bozeman, 
where  extractions  as  high  as  ninety-six  per  cent,  were  made  in  a  quarter  of 
an  hour  with  a  cyanide  solution.  A  company  of  Bozeman  men  arranged 
with  the  owners  to  handle  the  tailings  (at  Iron  Rod)  on  a  percentage  of  their 
assay  value.  F.  W.  Traphegan,  Ph.  D.,  went  to  work  to  elaborate  a  scheme 
whereby  the  material  could  be  handled,  and  decided  on  a  combined  system 
of  agitation  and  percolation,  the  slimes  to  be  coagulated  by  the  use  of  lime 
during  agitation,  when  percolation  could  be  carried  on  without  difficulty. 
The  agitator  was  built,  a  charge  put  in,  material  was  flocculated  and  every- 


Black  Hills  Mining  Men's  Association.  65 

thing  worked  nicely  until  attempt  was  made  to  draw  the  fluid.  Every  affort 
to  secure  percolation  of  the  charge  resulted  in  absolute  failure."  Mr.  Alder- 
son  continues,  "I  was  impressed  with  the  fact  that  the  moment  agitation 
ceased  the  sand  and  slimes  sought  the  bottom  of  the  vat  and  the  fluid  rode 
the  top.  I  remarked  that  every  successful  invention  was  the  result  of  work- 
ing with  nature,  and  that  successful  handling  of  slimes  would  come  about 
from  drawing  the  fluid  from  the  top,  where  it  naturally  came.  The  percola- 
tion was  discontinued  and  decantation  was  attempted,  and  the  mechanical 
difficulty  in  the  way  of  treating  the  slimes  soon  overcome."  You  will  notice 
that  Montana  men,  in  the  work  of  solving  the  slimes  problem,  were  contem- 
poraneous with  South  African  chemists,  and  did  not  copy  from  them. 

During  1897  and  1898  I  was  in  the  employ  of  Mr.  Alderson  in  his  cyanide 
works  in  Montana,  and  had  the  benefit  of  all  his  varied  experience  at  a  num- 
ber of  places.  In  1899  Capt.  Bullock  employed  me  to  make  experiments" 
on  the  Gunnison  ores  to  determine  their  amenability  to  cyanide  and  the 
work  was  successful  enough  to  warrant  the  building  of  a  mill.  Mr.  Bullock, 
as  manager  for  the  Dakota  Mining  and  Milling  Company,  said  to  me  that 
there  was  an  old  stamp  mill  in  Central  City  he  could  get.  I  told  him  that  a 
stamp  mill  was  my  choice,  and  so  it  was  determined  to  fit  it  up  for  use,  and 
I  drew  the  plans.  Mr.  Bullock  gave  to  me  his  confidence,  and  the  difficulties 
were  freely  discussed  as  they  occurred  and  were  suggested  to  him,  and  always 
when  he  said  slimes,  which  he  frequently  did,  I  quoted  Butters  and  said, 
"The  more  slimes  the  better."  My  experience  in  Montana  had  led  me  to 
think  with  confidence  of  being  able  to  treat  them  successfully.  But  I  never 
mentioned  that  I  intended  to  use  cyanide  solution  in  the  mortars,  for  I  was 
afraid  he  would  veto  it,  and  I  believed  it  to  be  the  key  to  the  successful 
treatment  of  the  ore. 

Mr.  Bullock  would  generally  end  our  discussion  of  ways  and  means  by 
saying,  "Well,  I  believe  you  know  what  you  are  doing  and  I  will  leave  it  all 
to  you."  In  determining  to  use  cyanide  in  the  mortars  I  had  but  one  re- 
corded success  to  give  me  confidence.  Mr.  Frank  Merricks  in  a  paper  read 
at  a  meeting  of  the  Institute  of  Mining  and  Metallurgy,  London,  this  same 
year,  1899,  said,  "About  eighteen  months  ago,  at  the  Crown  Mine,  New 
Zealand,  wet  crushing  experiments  were  made  with  cyanide  solution  passing 
through  the  mortars.  The  method  of  handling  the  slimes  and  the  results 
obtained,  have  not  been  made  public,  but  are  presumed  to  have  been  satis- 
factory as  the  plant  has  been  changed  to  wet  crushing."  This  is  all  that  was 
said  regarding  the  method.  Mr.  Alderson  had  not  used  this  method  nor 
suggested  its  use.  The  mill  at  Central  City  was  built  on  level  ground  and 
the  plan  was  to  catch  the  pulp  in  a  hopper  and  elevate  it  into  a  vat  where 
it  was  stirred  by  a  Alderson  propeller  blade  agitator.  The  mill  was  started 
up  early  in  October,  1899.  I  did  not  put  cyanide  into  the  mortars  until  the 
filling  of  the  second  vat.  Mr.  Bullock  came  in  in  a  few  hours  afterward  and  one 
of  the  mill  men  told  him.  He  came  to  me  and  said,  "You  are  putting  cyan- 
ide into  the  batteries."  I  replied,  "Yes."  Nothing  more  was  said  by  either 
of  us  until  the  results  were  known.  The  extraction  and  saving  were  just  as 
good  from  the  very  start  as  during  any  subsequent  work.  But  there  were 


66  Black  Hills  Mining  Men's  Association. 

mechanical  difficulties  to  overcome  in  order  to  increase  the  capacity  and 
secure  economy. 

One  of  the  first  of  these  was  the  method  of  lifting  the  pulp  up  into  the 
agitator  vat  from  the  mortars.  It  had  been  planned  to  use  a  centrifugal 
pump,  but  some  one  suggested  a  steam  jet.  It  so  happened  that  just  at 
this  time  the  papers  were  full  of  the  great  efficiency  of  hot  alkaline  solution 
in  the  treatment  of  gold  ores.  It  (Joes  seem  plausible  when  we  remember 
what  scientists  say  on  the  subject.  LeCoute  says,  "water  at  752  degrees 
F.  reduces  to  a  pasty  condition  nearly  all  ordinary  rocks — and  in  the  pres- 
ence of  alkali,  even  in  small  amounts,  the  same  result  is  produced  at  as  low 
as  300  degrees."  Water  boils  at  212  degrees  F.,  so  you  see  how  a  great 
metallurgical  result  might  be  expected  without  using  excessive  heat,  so 
much  so  that  hardly  a  year  passes  in  which  we  do  not  hear  of  some  such 
attempt.  I  had  no  faith  in  a  commercial  success  through  such  agencies 
for  the  reason  that  the  alkaline  solutions  are  to  no  considerable  extent  selec- 
tive in  their  effects,  and  no  metallurgical  reagents  which  are  not  selective 
can  be  successfully  applied.  This  proved  true  in  this  case,  and  before  many 
days  the  solutions  became  so  foul,  so  loaded  with  base  salts,  that  a  change 
was  necessary;  the  expense  of  using  steam  in  this  way  also  made  it  im- 
practicable, and  a  centrifugal  pump  was  substituted.  The  first  method  of 
treatment  tried  was  agitation  of  the  entire  battery  product,  which  was  then 
discharged  into  a  second  vat  and  the  solution  drawn  both  by  percolation  and 
decanting. 

This  proved  all  right  in  saving  of  the  values,  but  the  sands  would  at 
times  be  so  heavy  and  packed  so  solid  they  could  not  be  agitated,  then  the 
ore  would  change  and  the  pulp  be  so  light  and  slimy  that  nearly  all  the  solu- 
tion would  have  to  be  drawn  off  by  decanting.  To  provide  better  for  this 
varying  condition  another  and  larger  vat  sixteen  feet  by  eight  feet,  was  built 
and  the  slimes  washed  out  into  it,  passing  through  the  centrifugal  pump,  by 
an  agitation  overflow,  and  then  the  sands  discharged  into  the  percolation  vat. 
The  mill  was  an  old  antiquated  pattern  of  the  seventies,  and  short  in  power 
and  when  agitating,  the  batteries  had  to  be  hung  up.  It  was  seen  that  if 
the  separation  of  sands  from  slimes  could  be  made  outside  of  the  agitator 
and  only  the  slimes  treated  in  it,  that  the  running  time  of  the  batteries  could 
be  nearly  doubled.  -To  accomplish  this  a  V  box  was  introduced  and  accom- 
plished all  that  was  expected  from  it.  The  sands  thus  separated  were 
treated  by  the  conventional  methods.  The  slimes  were  treated  in  the  Alder- 
son  agitator  for  three  or  four  hours,  then  discharged  through  the  centrifugal 
pump,  with  barren  solution  wash,  into  the  big  slime  vat  where  settling  and 
decanting  took  place.  It  all  looks  very  simple  as  finally  worked  out,  but 
before  it  was  accomplished  the  management  put  in  many  a  twenty-four  hour 
shift  and  Capt.  Bullock  walked  up  to  Central  many  times  while  the  morning 
star  was  still  shining. 

It  is  not  claimed  that  any  of  the  work  done  represents  the  best  prac- 
tice, but  that  the  results  obtained  were  secured  in  the  way  stated. 

I  contributed  to  the  Mining  and  Scientific  Press  of  March  10  and  Sep- 
tember 8,  1900,  articles  giving  full  details  of  this  work.  On  January  14, 


Black  Hills  Mining  Men's  Association.  67 

1903,  I  wrote  to  the  publisher  saying  that  so  far  as  I  knew  the  above  articles 
by  me  gave  the  detail  of  the  first  successful  practice  of  wet  crushing  in  cya- 
nide solution  published  in  the  United  States,  and  asking  that  if  he  knew  of 
any  prior  successful  work  being  done  to  mention  it.  In  reply  he  wrote: 

SAN  FRANCISCO,  CAL.,  January  20,  1903. 
MR.  JOHN  M.  HENTON, 

Deadwood,  S.  D. 

Dear  Sir: — Replying  to  your  inquiry  of  the  14th  inst.,  so  far  as  we  are 
able  to  investigate,  the  stand  you  take  is  in  accordance  with  the  facts.  I 
have  not  yet  been  able  to  note  any  account  of  the  real  experiments  in  Cali- 
fornia referred  to,  but  the  subject  will  be  given  further  attention.  With 
personal  regards,  Very  truly  yours, 

J.  F.  HALLORAN. 

Mill  men  engaged  in  dry  crushing,  where  fine  crushing  is  necessary, 
have  the  slimes  problem  to  deal  with  and  Mr.  W.  A.  Watson  has  written  to 
me  a  very  interesting  letter  on  the  subject  of  treating  this  dust,  which  I 
take  pleasure  in  giving  a  synopsis  of: 

DENVER,  COLO.,  April  17,  1903. 
MR.  JOHN  M   HENTON, 

Deadwood,  S.  D. 

Dear  Sir: — Your  letter  under  date  of  April  16th  reached  me  this  even- 
ing, and  I  am  pleased  to  acknowledge  receipt,  and  I  wish  to  applaud  the 
action  of  the  Mining  Men's  Club  of  the  Black  Hills  in  getting  together  for 
discussion  of  ideas,  and  the  presentation  of  views  and  practices.  *  *  * 

The  old  Golden  Reward  mill,  as  all  Black  Killers  know,  was  a  dry  crush- 
ing plant,  and  we  had  the  usual,  or  possibly  more  than  the  usual  amount 
of  dust.  *  *  *  This  was  overcome  to  a  large  extent  by  installing  an 
ordinary  "Buffalo"  exhaust  fan,  the  same  as  is  used  in  handling  shavings 
and  saw  dust  in  a  planing  mill.  This  dust  at  first  was  run  into  a  room  where 
a  jet  of  exhaust  steam  was  turned.  The  collecting  of  the  dust  was  remark- 
ably well  done  in  this  way.  Our  idea  was  to  make  brick  of  this  mass,  and 
to  ship  it  to  the  smelter.  We  did  make  a  large  quantity  of  brick ;  but  when 
we  learned  of  the  treatment  charge,  the  cost  to  brick  and  to  load  into  cars 
we  arrived  at  the  fact  that  we  "were  up  against  it  hard  and  fast."  *  *  * 

After  the  days  of  mud  we  went  back  to  the  dry  dust,  which  was  col- 
lected in  the  upper  part  of  a  large  bin  by  means  of  triangular  or  trough- 
shaped  screens  made  of  large  sheets  of  burlap.  By  arranging  them  at  very 
acute  angles  we  were  able  to. get  into  our  bag  house"  a  large  number  of 
square  yards  of  burlap,  and  at  the  same  time  permitting  these  bags  to  free 
themselves  of  the  collected  dust,  and  to  discharge  into  the  hoppered  bin 
below.  The  exhaust  from  this  bag  house  was  passed  through  a  long  hori- 
zontal dust  collector  three  feet  deep  by  four  feet  wide  with  hopper  bottom 
and  discharge  slides  which  emptied  into  a  car.  This  collector  extended 
through  twice  the  length  of  the  mill,  140  feet,  if  I  remember  correctly.  The 
whole  collector  was  dust  tight  and  within  it  was  hung  strips  of  burlap  three 
feet  wide  extending  the  full  length  of  the  collector,  fastened  only  at  the  top 
and  the  inlet  end,  resembling  somewhat  a  book  opened  to  separate  the  leaves 
and  then  suspended  from  the  back.  These  leaves  were  arranged  one  inch 
apart,  the  inlet  end  being  securely  fastened,  but  the  opening  between  each 
leaf  free  for  the  passage  of  air  to  enter.  The  air  caused  a  waving  motion  of 
the  burlap  which  arrested  the  remaining  dust  almost  completely.  Between 
the  hoppers  at  short  distances,  a  partition  was  extended  .up  to  the  lower 
edge  of  the  burlap.  This  was  to  compel  the  air  to  pass  between  the  leaves 
and  not  under. 


Black  Hills  Mining  Men's  Association. 


Our  slime  machines  were  two  in  number,  and  consisted  of  two  steel 
tanks,  thirteen  feet  in  diameter  by  four  feet  deep.  All  of  our  machines  and 
the  general  arrangements  were  built  to  comply  with  the  available  space  in 
the  mill  building.  These  tanks  would  have  been  better  had  they  been 
greater  in  diameter  and  three  times  the  depth.  Each  tank  had  a  "hollow 
shafting  which  stood  vertically  in  the  center  and  extended  about  two  feet 
above  the  top,  and  was  fitted  to  a  bevel  gear  which  was  driven  by  a  belt. 
Each  machine  had  its  clutch  for  starting  and  stopping.  Just  under  the 
driving  gear  were  two  cross  arms  from  which  were  suspended  by  chains, 
sheets  of  boiler  plate  one-half  inch  by  six  inches  by  eighteen  inches,  which, 
when  hanging  vertically,  reached  within  six  inches  of  the  bottom,  and  arranged 
upon  the  cross  arms  in  such  a  manner  that  the  whole  contents  would  be 
thoroughly  mixed.  At  the  bottom  of  the  hollow  shaft  were  fitted  four  one- 
inch  perforated  pipes,  each  extending  outward  to  the  circumference  of  the 
tank.  The  perforations  were  one-sixteenth  of  an  inch  in  diameter,  and 
arranged  about  one  inch  apart.  Each  tank  was  arranged  with  an  overflow 
box,  which  carried  the  clear  supernatant  liquid  into  the  solution  tanks. 

A  charge  of  three  to  four  tons  of  dry  slimes  was  dumped  into  the  tank 
and  enough  cyanide  solution  of  a  strength  0.3  to  0.60  per  cent,  added  to 
make  the  mass  the  consistency  of  thin  mortar,  the  mixing  paddles  were  low- 
ered into  the  tank,  and  the  whole  mass  thoroughly  mixed  and  agitated  from 
three  to  six  hours.  The  mixing  device  was  then 'raised  and  allowed  to  hang 
at  rest.  The  hollow  shaft  continued  to  revolve  very  slowly  and  the  charge 
allowed  to  settle  a  foot  or  more  and  then  the  weak  cyanide  solution  was 
allowed  to  pass  into  the  mass  down  through  the  hollow  shaft  and  out  the 
perforations  in  the  lower  pipes,  under  low  gravity  pressure.  The  richer 
solution  was  gradually  displaced  by  the  weaker,  and  overflowed  and  run 
directly  to  the  gold  solution  tank,  and  from  thence  to  precipitating  boxes. 
The  weak  solution  was  followed  by  water.  *  *  * 

W.  A.  WATSON. 

A  number  of  bright,  practical  men  are  engaged  in  trying  to  improve 
the  methods  of  slime  treatment  as  practiced  today,  and  we  may  expect  that 
some  one  or  possibly  more,  will  ultimately  make  a  marked  success.  The 
fact  remains,  however,  that  so  far  as  relates  to  the  mill  practice  as  com- 
mercially carried  on,  but  little  advance  has  been  made  over  that  described  by 
Chas.  Butters.  The  economic  difficulties  in  the  treatment  of  low  grade  slimes 
are  great  and  it  will  be  a  marvel  if  the  Homestake  company,  for  instance,  suc- 
ceeds in  treating  at  a  profit  a  $1.00  slime.  It  is  the  economy  of  the  stamp  mill 
as  an  ore  pulverizer  that  gives  to  wet  crushing  in  cyanide  solutions  the 
prominence  it  has  received,  and  any  new  or  improved  method  of  slimes  treat- 
ment must  bring  with  it  this  same  element  of  advantage,  economy  of  opera- 
tion and  maintaining  in  efficient  working  order. 


Black  Hill*  Mining  Meris  Association. 


CYANIDING  PRACTICE  AT  THE  MAITLAND  PROPERTIES. 

BY  JOHN  GROSS,  MILL  SUPERINTENDENT  AND  CHEMIST. 
[Paper  read  before  Black  Hills  Mining  Men's  Association,  April  20th,  1904.] 

INTRODUCTORY. 

The  group  of  claims,  comprising  over  1,100  acres,  located  at  Maitland* 
in  the  Ida  Gray  Mining  District,  Lawrence  County,  South  Dakota,  owned 
by  Alexander  Maitland,  are  being  developed  and  operated  by  the  owner. 

Prior  to  the  acquisition  of  this  property  by  the  present  owner,  com- 
paratively little  work  had  been  done  and  but  little  was  really  known  of  this 
district.  Within  the  last  two  years,  however,  development  has  opened  up 
some  very  promising  ore  chutes  and  the  property  is  today  in  excellent  shape. 
The  ores  so  far  encountered  are  the  so-called  Potsdam  siliceous  ores 
of  the  flat  formation  lying  on  top  of  the  Cambrian  quartzite;  both  oxidized 
and  blue,  or  unoxidized,  ores  are  met  with;  a  small  amount  of  the  blue  ores 
are  unavoidably  sent  to  the  mill,  special  care  is  taken,  however,  to  send  only 
the  oxidized  ores  for  the  cyanide  treatment;  the  sulphur  in  the  mill  ore  will 
run  from  one  to  two  per  cent. 

The  ores  are  close  grained  and  hard  and  have  given  quite  a  little  trouble 
in  their  treatment.  Pyrrhotite  and  iron  pyrites  exist  in  about  equal  pro- 
portions. Arsenic  and  traces  of  copper,  antimony  and  tellurium  are  found 
and  bismuth  has  been  detected  in  the  bullion.  The  silver  contents  pre- 
dominate slightly  over  the  gold  in  the  low  grade  while  the  reverse  is  generally 
true  in  the  high  grade  ores. 

The  following  analyses  give  a  fair  idea  of  the  general  character  of  these 
ores: 

Oxidized  ores  from  two  different  mill  samples,  covering  a  period  of 
several  months. 

No.  1  No.  2 

Au 0 . 56  Ozs.         0 . 69  Ozs. 

Ag 1.03  Ozs.         1.50  Ozs. 

SiO2 70.95%  73.20% 

Fe 10.30%  10.40% 

S : 1.66%  0.63% 

As 0.30%  0.00% 

Sb...  Trace  0.00% 

Te 0.002  %     Trace 

Cu 0.02%  0.004% 

Zn 0.00%  0.00% 

Mn Trace  0.75% 

A1203 4.30%  2.14% 

CaO 3.40%  3.20% 

MgO 1 .02%         Not  Determined. 

*Formerly  known  as  Garden  City. 


70 


Black  Hills  Mining  Men's  Association. 


Blue  ores  from   two   general  samples: 


No.  1 


Au. 


0.63  Ozs. 

2.00  Ozs. 

SiO2 65.38% 

Fe 13.40% 

S 11.40% 

As 0.90% 

Sb .  .  : Trace 

Te 0.003 

Cu.  ...-.....,.;... 0.02% 

Zn 0.00% 

Mn Trace 

A12O3 5.43% 

CaO 2.10% 

MgO 0.20% 


No.  2 

0.85  Ozs 

6. 08  Ozs. 
80.00% 

7.50% 

4.40% 

2.00% 

0.00% 
Trace 

0.004 

0.00% 

0.54% 

1.79% 

1.70% 
Not  determined. 


High  grade  ores,  No.  1  being  a  blue  and  No.  2  a  brown  ore: 


No:  2 

2.00  Ozs. 

0.62  Ozs. 
84.80% 

7.50% 

0.75% 

0.00% 

0.00% 
Trace 

0.008% 

0.00% 

0.96% 

1.02% 

0.90% 
Not  determined 


No.  1 

Au 3.35  Ozs. 

Ag 1.75  Ozs. 

SiO2 80.90% 

Fe 9.94% 

S 4.53% 

As 0.29% 

Sb Trace 

Te 0.007% 

Cu .^. 0.013% 

Zn Trace 

-     Mn Trace 

A12O3 1.70% 

CaO 0.50% 

Mgo Trace 

Early  in  1902  the  building  of  a  forth  stamp  wet  crushing  cyanide  mill 
was  begun  and  finally  placed  in  commission  by  January  1st,  1903.  The 
treatment,  as  outlined,  was  to  crush  in  a  cyanide  solution,  separating  the 
sands  from  the  slimes  and  the  treatment  of  the  slimes  by  agitation  and  de- 
cantation. 

The  ore  is  trammed  from  the  shaft,  .300  feet  east  of  the  mill  through  a 
covered  tramway  and  delivered  to  the  crusher  bin. 

The  boilers  are  all  consolidated  near  the  hoist,  while  nearby  a  well 
equipped  machine  and  blacksmith  shop  are  located. 

A  50,000  gallon  water  supply  tank  on  the  hill  back  of  the  mill  supplies 
the  necessary  water  for  the  mill  and  boilers  and  is  obtained  entirely  from 
the  mine  workings. 

MILL  PRACTICE. 

Accompanying  this  paper  is  a  metallurgical  plan  of  mill  showing  the 
complete  treatment  of  the  ore. 

All  figures  given  in  this  paper  are  based  on  a  daily  tonnage  of  100  to 
110  tons  as  now  maintained.* 


*Since  this  paper  was  written  the  capacity  of  the  mill  has  been  increased 
to  very  close  toj(120  tons  per  day. 


Black  Hills  Mining  Men's  Association.  71 

CRUSHING  THE  ORE. 

The  ore  as  it  comes  from  the  mine,  carrying  an  average  of  eight  per 
cent,  moisture  is  delivered  to  crusher  bin  of  150  tons  capacity. 

The  crusher  is  a  24x13  inch  Blake  running  at  260  revolutions  per  minute 
and  is  set  to  crush  to  a  size  that  will  pass  through  a  one  and  one-half  to  two 
inch  ring.  The  average  time  of  running  the  crusher  is  seven  hours  per  day 
equal  to  a  capacity  of  fifteen  tons  per  hour. 

We  have  no  figures  at  hand  on  costs  of  iron  used  on  the  crusher  as  none 
of  the  plates  have  been  worn  out. 

The  crushed  ore  passes  to  the  elevator  where  it  is  elevated  forty-four 
feet  for  delivery  to  the  battery  bins. 

In  the  original  mill  installation  a  continuous  type  bucket  elevator 
traveling  100  feet  per  minute  was  provided  but  was  soon  discarded  after 
handling  9,300  tons  of  ore;  the  links  had  worn  out  causing  the  elevator 
to  fall  into  the  pit  on  several  occasions. 

A  fourteen  inch  eight-ply  rubber  belt  is  now  used,  traveling  350  feet  per 
minute;  to  give  longer  life  to  the  belt  it  is  now  reinforced  between  the 
buckets  with  old  pieces  of  belt  which  take  the  roughest  wear,  but  one  belt 
has  so  far  been  worn  out  after  having  handled  16,965  tons  at  a  cost  of  0.91 
cents  per  ton  ore.  Twelve  inch  buckets  are  spaced  eighteen  inches  apart 
on  the  belt.  No.  10  steel  buckets  were  first  used  and  handled  16,965  tons 
at  a  cost  of  45  cents  per  ton  ore. 

Malleable  iron  buckets  proved  to  be  too  light  for  the  work  and  handled 
8,080  tons  at  a  cost  of  0.76  cents  per  ton.  We  are  now  using  No.  6  steel 
buckets  but  have  no  figures  on  these  yet. 

The  ore  as  it  falls  from  the  elevator  head  to  the  battery  bins  is  cut  by 
an  automatic  sampler  which  cuts  out  one-fiftieth  of  the  ore  and  delivers  it 
to  the  sample  room  where  it  is  cut  down  daily. 

STAMPS. 

The  battery  bins,  of  which  there  are  two  ofjlSO  tons  capacity  each,  are 
located  one  behind  each  set  of  twenty  stamps.  Hung  challenge  feeders  are 
used  and  are  giving  very  good  satisfaction. 

The  mortar  is  narrow,  single  issue  type,  and  a  six  inch  discharge  is  main- 
tained by  means  of  chuck  blocks.  Thirty  mesh,  No.  28  wire  screens  were 
originally  used,  but  have  been  replaced  by  26x13  mesh,  No.  26  wire;  this 
screen  giving  a  longer  opening  does  not  choke  so  readily;  the  screens  used 
are  rolled,  which  also  helps  to  keep  the  holes  open.  The  life  of  one  of  these 
screens  is  about  fifty  days. 

The   stamp   weights   are   as   follows: 

Pounds 

Shoe 150 

Boss  head 250        i' 

Stem 375 

Tappet 135 

Total  weight  of  stamp,  new 910 


72  Black  Hills  Mining  Men's  Association. 

Ten  cams  with  Canda  fasteners  are  on  one  shaft.  Ninety-seven  drops 
per  minute  of  seven  to  eight  inches  are  given,  the  order  being  1-3-5-2-4. 

Chrome  shoes  and  dies  are  now  being  used  but  other  makes  have  been 
and  are  to  be  experimented  upon. 

A  Chrome  shoe  wears  from  ninety  to  ninety-five  days,  crushing  250 
tons  of  ore  at  a  cost  of  4.90  cents  per  ton.  A  cast  iron  shoe  wears  from 
thirty-five  to  forty  days  crushing  105  tons  of  ore  at  a  cost  of  4.95  cents 
per  ton. 

We  have  no  records  as  yet  on  Chrome  dies.  Cast  iron  dies  wear  forty 
days,  crushing  105  tons  ore  at  a  cost  of  3.28  cents  per  ton.  Wilson  forged 
steel  dies  wear  105  days,  crushing  280  tons  ore  at  a  cost  of  3.06  cents  per  ton. 

The  above  figures  on  shoes  and  dies  cover  a  period  of  eight  months 
running. 

The  battery  solution  is  kept  at  a  strength  of  1.2  to  1.3  pounds  of  KCy 
and  a  protective  alkalinity  corresponding  to  from  0.8  to  1.0  pounds  of 
NaOH  per  ton.* 

The  lime  is  fed  with  the  ore  into  the  battery.  An  analysis  of  the  lime 
used  is  given  below: 

CaO 92.0% 

MgO 0.4% 

Al2O3+Fe2Oa 1.2% 

Insoluble 2.4% 

H20+C02..  ..  1.1% 

The  stamp  duty  is  not  high,  for  the  last  six  months  of  1903,  the  average 
was  2.66  tons;  this  has  now  been  increased  very  close  to  three  tons.  The 
amount  of  solution  going  to  the  battery  is  between  four  and  five  tons  to 
one  ton  of  ore;  this,  together  with  the  hardness  and  compactness  of  the  ore 
accounts  largely  for  the  small  stamp  duty. 

The  stamps  deliver  a  product  carrying  about  sixty  per  cent  sands,  and 
forty  per  cent  slimes.  The  material  that  we  call  slimes  is  that  portion  of 
the  ore  that  will  make  water  muddy;  sands,  no  matter  how  fine,  will  not 
cause  water  to  appear  muddy. 

The  loss  of  time  on  battery  running  for  the  last  seven  months,  when 
the  mill  started  working  full  shift  has  been  5.8  per  cent. 

SEPARATION. 

The  separation  of  the  slimes  from  the  sands  is  one  of  the  most  vital, 
if  not  the  most  vital  one,  in  the  wet  crushing  process  and  several  systems 
were  tried  but  found  to  be  inadequate. 

In  the  separating  system  that  we  are  at  present  using  we  have  found 
it  to  be  advisable  to  make  a  clean  sand  rather  than  a  clean  slime;  a  sand 
charge  with  five  per  cent  or  higher  in  slimes  giving  us  a  low  leaching  rate 
so  that  we  are  making  this  clean  sand  at  the  expense  of  throwing  some 
sands  into  the  slimes;  these  sands  are,  however,  very  fine  and  cause  no 

*But  two  solutions  are  used  in  the  mill,  the  battery  solutions  as  noted 
above,  assaying  about  50  cents  per  ton,  and  the  barren  solution  with  a 
strength  of  1.5  to  1.6  pounds  KCy  and  a  protective  equivalent  of  1.0  to 
1.2  pounds  of  NaOH  per  ton  of  solution. 


Black  Hills  Mining  Men's  Association.  73 

trouble  in  the  slime  department  and  assay  after  treatment  the  same  as  the 
slimes  proper. 

The  pulp  that  the  battery  delivers,  flows  to  two  Frenier  sand  pumps 
54x10  inches,  making  nineteen  revolutions  per  minute,  and  is  raised  twenty 
and  one-half  feet  to  a  box  provided  with  a  screen  to  catch  any  foreign 
substance,  thus  preventing  the  choking  of  the  cones;  this  box  delivers 
the  pulp  to  two  upper  cones  and  is  intended  primarily  to  take  care  of  the 
intermittent  discharge  of  the  sand  pumps,  giving  a  more  steady  feed  to 
the  cones. 

These  two  upper  cones  are  simple  in  construction,  forty-two  inches  in 
diameter  at  the  top  and  having  vertical  sides  for  twelve  inches  down,  at 
which  point  the  cone  starts  at  a  sixty-degree  slope,  ending  in  a  six-inch 
diameter  sorting  column  with  a  two-inch  discharge  at  bottom  provided 
with  a  cock. 

The  sands,  containing  twenty-five  to  thirty  per  cent  slimes,  discharge 
at  the  bottom  of  the  two  upper  cones,  combine  and  flow  to  a  single  cone, 
the  same  size  as  the  upper  ones,  but  provided  with  an  upward  current  of 
solution.  This  upward  current  is  taken  from  the  battery  solution  stock 
tank. 

The  sands  discharging  at  the  bottom  contain  from  one  to  two  per  cent 
of  slimes  and  go  direct  to  sand  vats. 

The  slimes  overflow  from  the  three  cones  contain  from  fifteen  to  twenty- 
five  per  cent  sands  of  which  only  a  small  portion  will  stay  on  a  150  mesh 
screen. 

The  products  going  to  sand  and  slime  vats  from  the  cones  amount 
each  to  very  close  to  fifty  per  cent  of  the  original  ore;  the  average  since 
the  cone  system  was  installed,  eight  months  ago,  has  been  48.2  per  cent 
to  sand  and  51.8  per  cent  to  slime  vats. 

SAND  TREATMENT. 

The  clean  sands  from  the  lower  cone  issuing  with  2.8  parts  of  solution 
to  one  part  sand  flow  through  launder  with  a  grade  of  seven  in  100  to  the 
distributor  over  the  sand  vats.  The  amount  of  solution  with  the  sands 
coming  from  the  cone  is  not  sufficient  to  carry  same  through  launder  and 
keep  the  distributor  open  and  running;  to  overcome  this,  sufficient  solution 
is  added  in  the  launder  to  bring  it  up  to  at  least  five  of  solution  to  one  of 
sands. 

The  distributor  is  of  the  Butters  type,  ball  and  roller  bearings,  with 
six  arms. 

The  sand  vats,  of  which  there  are  six,  are  thirty  feet  in  diameter  by 
six  feet  deep,  having  a  lattice  filter  frame;  eight-ounce  duck  cloths  are  used 
on  top  of  cocoa  matting;  the  eight-ounce  duck  has  been  found  to  be  more 
satisfactory  than  the  heavier  grades. 

The  sand  vats  hold  140  tons  and  are  filled  in  about  sixty  hours. 

The  system  of  filling  the  sand  vats  through  a  vat  full  of  solution  has 
been  discarded  in  favor  of  dry  filling,  i.  e.,  the  vat  contains  no  solution  when 
starting  to  load  and  all  incoming  solution  with  the  sands  is  allowed  to  drain 


74  Black  Hills  Mining  Men's  Association. 

off  as  rapidly  as  it  enters,  keeping  practically  a  dry  surface  on  top  of  the 
sands  ;  this  gives  a  better  leaching  product  as  the  slimes  with  the  sands 
are  evenly  distributed  throughout  the  charge,  this  does  not  occur  in  filling 
through  a  vat  full  of  solution.  This  method  of  filling,  moreover,  gives  a 
more  porous  charge,  the  average  weight  of  a  cubic  foot  of  sands  as  filled 
into  the  vats  being  but  ninety-two  pounds,  figured  from  the  last  eight  months 
run;  the  specific  gravity  of  the  original  ore  averaging  2.7. 

When  the  vat  is  filled  it  is  leveled  off  and  battery  solution  is  run  on 
for  an  average  of  ten  days ;  this  battery  solution  contains  a  small  amount 
of  slimes  which  form  a  coating  on  top  of  the  charge  requiring  an  occasional 
light  raking  over  to  keep  a  satisfactory  leaching  rate.  The  battery  solu- 
tion is  followed  by  barren  solution  treatment  for  about  six  days  more  when 
the  vat  is  allowed  to  drain  and  a  wash  water  of  fifteen  tons  is  put  through; 
the  sand  is  now  ready  for  sluicing,  requiring  from  100  to  150  tons  of  water 
for  this  purpose. 

An  average  of  a  large  number  of  sand  vats  gives  900  tons  battery  solu- 
tion and  450  tons  of  barren  solution  for  one  sand  vat  'treatment,  exclusive 
of  solution  filtering  through  charge  while  filling  which  amounts  to  ap- 
proximately 700  tons.  This  large  amount  of  solution  (being  nearly  ten 
tons  to  one  ton  of  sand)  together  with  a  total  treatment  time  of  about 
sixteen  days  has  been  found  necessary,  experiments  showing  that  a  large 
volume  of  weak  solution  kept  leaching  through  the  charge  as  quickly  as 
possible  is  essential  to  a  satisfactory  extraction. 

SLIME  TREATMENT. 

The  overflow  from  the  cones  flows  to  two  loading  vats  which  are  filled 
alternately. 

There  are  eight  slime  vats  (including  the  two  for  loading)  twenty-four 
feet  in  diameter  and  twelve  feet  deep  all  of  which  are  connected  to  two 
No.  4  centrifugal  pumps  which  can  deliver  to  any  one  of  the  slime  vats. 
The  centrifugal  pumps  are  four-inch  suction  and  four-inch  discharge  running 
at  550  revolutions  per  minute  and  handle  fifty  tons  of  wet  pulp  per  hour. 
Quite  a  large  amount  of  experimenting  has  been  done  on  the  transferring 
and  agitation  of  the  slimes  by  compressed  air  replacing  the  work  done  by 
the  centrifugals,  but  these  experiments  are  not  yet  sufficiently  advanced 
to  be  of  value. 

The  loading  vats  are  provided  with  a  partition  through  the  center  of 
the  vat  going  down  to  within  thirty  inches  of  the  bottom,  thus  allowing 
the  slimes  to  settle  sufficiently  so  that  the  clear  solution  may  be  decanted 
from  one  side  of  the  partition  while  the  vat  is  being  filled  from  the  other 
side.  The  time  of  filling  one  of  the  vats  is  twelve  hours,  when  the  stream 
is  turned  into  the  other  loading  vat. 

The  slimes  going  into  loading  vat  have  twelve  tons  of  solution  to  each 
ton  of  dry  slimes,  the  capacity  of  the  vat  being  150  tons  of  solution,  it  follows 
that  during  a  loading  of  twelve  hours  150  tons  or  half  of  the  incoming  solu- 
tion has  been  decanted  off. 


Black  Hills  Mining  Men's  Association.  75 

This  loading  vat  just  filled  is  decanted  as  close  as  possible  and  transferred 
to  vat  No.  1  by  the  centrifugal  pumps,  barren  solution  being  added  at  the 
same  time.  The  second  loading  vat,  after  decantation,  is  transferred  with 
barren  solution  to  vat  No.  2,  and  upon  the  decantation  of  these  two  vats 
Nos.  1  and  2,  the  contents  are  combined  and  pumped  to  a  third  vat;  two 
more  transfers  and  dilutions  are  given  with  barren  solution  and  finally  one 
with  water.  After  each  transfer  and  dilution  several  hours  of  agitation  are 
given  by  pumping  out  of  the  bottom  of  the  vat  and  discharging  into  the 
top  of  the  same  vat. 

It  will  be  noted  that  -the  two  largest  dilutions  are  obtained  on  half 
charges  when  the  contained  solutions  in  the  slimes  are  the  richest.  A 
charge  of  fifty-five  tons  of  dry  slimes  from  a  twenty-four  hours  run  gets  the 
following  dilutions: 

First  half  charge,  22£  tons,  1  dilution  of  85  tons. 

Second  half  charge,  22£  tons,  1  dilution  of  85  tons. 

Full  charge,  55  tons,  3  dilutions  of  55  tons. 

Making  a  total  dilution  of  335  tons  or  a  little  more  than  six  tons  of  bar- 
ren solution  to  one  ton  of  dry  slimes,  the  actual  figures  for  the  last  six  months 
being: 

6.38  tons  barren  solution  per  dry  ton  slimes. 

0.96  tons  wash  water  per  dry  ton  of  slimes. 

Theoretical  calculations  on  this  amount  of  dilution,  on  the  assumption 
that  the  extraction  has  all  taken  place  before  the  first  decantation,  and 
taking  the  value  of  the  barren  solution  at  ten  cents  per  ton,  the  dissolved 
gold  going  out  with  the  slime  tails  should  assay  from  twelve  to  twenty 
cents  per  ton  solution,  starting  with  a  head  slime  solution  of  $1.00  to  $2.00, 
however,  the  extraction  has  not  all  taken  place,  but  continues  slowly  through- 
out the  entire  treatment,  and  the  solutions  finally  going  out  with  the  slime 
tails  for  the  last  six  months  of  1903,  showed  an  average  value  of  46.1  cents 
per  ton,  with  an  average  value  of  a  little  less  than  $2.00  for  the  head  slime 
solution  and  a  value  of  10.6  cents  per  ton  of  the  barren  solution. 

The  decantations  are  brought  down  to  a  pulp  containing  from  fifty- 
five  to  sixty  per  cent  moisture.  After  the  decantation  of  the  wash  water 
the  top  layer  of  thinner  slimes  is  drawn  off  and  thrown  back  to  the  charge 
following,  in  this  way  we  obtain  a  dryer  slime  going  to  waste,  averaging 
for  the  last  six  months  of  1903,  46.7  per  cent  moisture. 

PRECIPITATION. 

Only  the  richer  solutions  from  the  sand  vats  go  to  the  gold  tank  for 
precipitation,  the  balance  of  sand  vat  solutions  and  all  the  decantations 
from  the  slimes  going  to  the  battery  solution  sump. 

All  standardizing  of  solutions  is  done  in  the  gold  tank  thus  getting 
the  benefit  of  the  higher  strength  solution  to  assist  in  the  precipitation, 
this  accounts  for  the  higher  strength  of  the  barren  solution  noted  before. 

Four  iron  zinc  boxes  are  used,  having  eight  compartments  with  a  capa- 


76  Black  Hills  Mining  Men's  Association. 

city  of  seven  cubic  feet  for  each  compartment,*  hand  cut  zinc  only  is  used 
as  it  offers  a  better  precipitating  medium  than  the  machine  cut;  it  is  true 
however  that  the  zinc  consumption  is  heavier  with  the  hand  cut  zinc.  Data 
for  the  last  six  months  of  1903  on  zinc  box  flow  is  given  below: 

Cub.  Feet        Tons  Sol.  Tons  Sol. 

Tons  Content  per  per  Cub. 

Solution  Zinc  Day  Foot  Zinc 

July 10,265  194  331  1.71 

August 15,130  188  488  2 . 60 

September 14,130  200 .  485  2  43 

October 14,777  212  477  2.25 

November 12,793  200  426  2. 13 

December 12,501  230  403  1 . 75 

Six  months  1903 204  435  2.13 

Having  the  measurements  of  the  zinc  box  flow  and  the  assays  on  the 
head  and  tail  solutions  we  are  enabled  to  keep  very  close  check  on  extrac- 
tions; the  actual  bullion  returns  exceed  the  precipitation  as  shown  by  the 
boxes  by  3.4  per  cent  average. 

Of  the  barren  solution  about  one-fourth  goes  for  sand  and  the  balance 
for  slime  treatment. 

The  zinc  consumption  for  the  last  six  months  of  1903  is  given  below: 

Lbs.  per  Ton  Lbs.  per  Ton  Sol. 

Ore  Treated  of  Zinc  Box  Flow- 
July 1.86  0.310 

August 1 . 08  0 . 291 

September 1 . 50  0 . 316 

October 1.15  0 . 267 

November 1 . 37  0.317 

December 1 . 19  0 . 300 

Six  months  1903 1.33  0.298 

BATTERY  SOLUTION. 

This  solution,  of  which  1,1.00  tons  per  day  are  used,  is  pumped  by  a 
Prescott  10x7xl2-inch  duplex  pump  to  stock  tank  at  top  of  mill,  and  is 
distributed  approximately  as  follows: 

tons 

To  battery 500 

To  cones 150 

To  launder 100 

To  sand  vats 350 

CLEANING  UP. 

Clean  ups  are  made  twice  a  month,  and  are  acid  treated  in  the  ordinary 
manner,  washed  and  filtered  and  taken  to  the  melting  room,  situated  at 

*Until  a  short  time  ago  there  were  in  addition  eleven  zinc  barrels  to 
assist  in  the  precipitation,  but  these  are  now  replaced  by  another  eight- 
compartment  iron  zinc  box  of  seventy-six  cubic  feet  total  capacity. 


Black  Hills  Mining  Men's  Association.  77 

some  distance  from  the  mill  proper,  where  they  are  dried  in  a  muffle  furnace 
and  fluxed  as  follows: 
10  parts  product. 
4  parts  bicarbonate  soda. 
1  part  borax. 

H  parts  sand  tails  (60%  available  SiO2). 
\  part  iron  scrap. 
I  part  flour  spar. 

This  flux  has  given  very  good  satisfaction,  the  charge  melting  easily 
and  quitely  and  giving  a  clean  and  liquid  slag.  The  melting  is  done  in  a 
No.  200  crucible  and  forced  draft  is  used. 

The  bullion  goes  to  the  U.  S.  Assay  Office  at  Deadwood,  and  the  slags 
are  shipped  to  Denver  smelters. 

Just  below  the  acid  tank  is  located  a  waste  sump  having  a  capacity 
of  twenty-five  tons  water,  into  which  all  of  the  solutions  from  the  acid  tank 
and  vacuum  filter  are  allowed  to  flow;  this  solution  after  the  first  clean  up 
assayed  $12.00  per  ton  in  soluble  gold,  but  now  rarely  assays  over  $2.00 
per  ton.  This  solution  is  treated  with  fine  zinc,  obtained  from  the  zinc 
lathe,  and  sulphuric  acid,  is  well  stirred  and  allowed  to  settle  after  action 
has  ceased,  when  it  is  found  that  about  ninety  per  cent  of  the  soluble  gold 
has  been  precipitated.  The  sweepings  around  the  zinc  boxes  after  a  clean 
up  are  also  thrown  into  this  waste  sump.  This  waste  sump  settlings  to- 
gether with  the  accumulations  of  mattes  is  taken  care  of  in  a  general  clean 
up  made  twice  a  year.  The  mattes  are  melted  down  with  scrap  iron,  sand 
and  a  small  amount  of  flux,  giving  a  bullion  high  in  copper  and  carrying 
about  eighty  parts  gold  and  600  parts  silver. 

All  sweepings  from  melting  room  and  all  ashes  that  happen  to  assay 
rich  enough  are  crushed  and  mixed  with  the  slag  shipments. 

CYANIDE  CONSUMPTION. 

The  cyanide  consumption  per  ton  of  ore  treated  for  the  last  eight  months 
is  given  below  both  for  the  chemical  and  mechanical  losses;  the  mechanical 
loss  being  that  going  out  in  waste  solutions.  The  lime  consumption  is  also 
appended: 

Chemical         Mechanical  Lime 

KCy  Cons.      KCy  Cons.  Cons. 

Ibs.  Ibs.  Ibs. 

July 0.93  0.67  7.18 

August 1.03  0.42  7.91 

September 1.07  0.46  7.36 

October 1.08  0.38  6.14 

November 0.82  0.62  5.48 

December 0.89  0.41  5.36 

Six  months  1903 0.98  0 . 49  6 . 54 

January,  1904 0.52  0.51  5.03 

February,  1904 0.80  0.39  5.95 


78  Black  Hills  Mining  Men's  Association. 

EXTRACTION  RESULTS. 

While  we  are  not  obtaining  a  high  extraction  on  our  ores,  we  have  the 
satisfaction  of  having  made  a  fairly  regular  improvement  from  month  to 
month.  Cyanide  tests  have  been  made  regularly  on  all  the  ore  going  to 
the  mill  for  the  past  four  months;  the  bullion  returns  exceed  the  test  ex- 
traction by  6.7  per  cent. 

The  following  is  a  compilation  of  extractions  from  the  starting  of  the 
mill,  bullion  and  slag  returns  being  quoted  separately: 

Gold%  in     Gold%  in  Total  Total 

Bullion  Slag  Gold%  Silver% 

First  half  1903 46.75  1.81  48.56  22.6 

July 50.23  1.39  51.62  26.8 

August ;..      58.09  0.49  58.58  26.6 

September 60.26  0.80  61.06  18.6 

October 63.44  0.49  63.93  17.8 

November 67.32  2.02  69.34  21.4 

December 68 . 23  1 . 64  69 . 87  49 . 2 


Second  half  1903 61.15  1.07  62.22  26.1 

January  and  February,  1904  ...      67.66  1.88  69.54  52.2 

Of  this  extraction  fifty-three  per  cent  is  obtained  in  the  battery,  twenty- 
four  per  cent  from  the  sand  leaching,  and  twenty-three  per  cent  from  the 
slime  treatment  as  figured  from  the  results  of  the  last  four  months.* 

COST  OF  TREATMENT. 

The  working  costs  of  a  plant  of  this  nature  naturally  vary  quite  a  little 
from  month  to  month,  as  all  expenses  incurred  are  taken  up  at  once  and 
charged  out,  and  where  these  expenses  cover  several  months  or  more  they 
cause  that  particular  month  to  have  an  unduly  high  cost  sheet;  an  average 
of  six  months  run  is  given  whereby  the  larger  part  of  this  discrepency  is 
eliminated: 

CRUSHER Power $0.018     • 

Labor 0.064 

Repairs,  etc 0.010 

$0.092 

SAMPLING Power 0 . 007 

Labor    0.012 

Repairs,  etc. 0.002 

0.021. 

STAMPS ,'.!'.  .  Power 0 . 296 

Labor 0.108 

Repairs,  etc 0.058 

Sand  pumps.  . 0.026 

0.488 

*Since  the  compilation  of  these  figures  considerable  improvements 
have  been  made,  bringing  the  average  gold  extraction  for  the  first  five 
months  of  1904  to  seventy-three  and  one-half  per  cent. 


80 

Black  Hills  Mining  Men's  Association. 

LEACHING 

.  Pumping  solution. 

0  051 

CHEMICALS  
PRECIPITATION 

Sluicing  sands  
Handling  slimes  
Labor  
Repairs,  etc  

Lime  
Cyanide  .  .  (  

Labor 

.    0.007 
.    0.019 
.    0.069 
.    0.013 

.    0.034 
.    0.368 

0  019 

0 

0 

.159 
.402 

i 

Zinc  
Repairs  etc. 

.    0.091 
0  003 

CLEAN  UP. 

.  Labor  .  . 

0  005 

0 

.113 

v''  •*• 

Assavin? 

Acid  
Fuel  
Fluxes  
Crucibles  
Repairs,  etc  

.    0.009 
.    ().00> 
.    0.005 
.    0.006 
.    0.004 

0 
0 

.034 
044 

Mill  Engineers 

0 

070 

Electric  Light 

0 

035 

General  Expense 

0 

.322 

Total  Expense  of  Milling  one  ton  of  ore $1 .789 

The  clean  up  cost  figures  very  close  to  8.5  cents  per  ounce  of  fine  bullion 
produced,  including  the  cost  of  marketing  the  bullion. 

In  the  above  costs  on  power,  the  fuel,  labor  and  necessary  repairs  to 
the  generation  of  steam  are  included,  and  the  division  of  the  power  is  based 
on  indicator  cards  taken  from  the  mill  engine,  the  average  cost  of  a  horse 
power  day  being  35  cents. 

The  costs  given  include  every  item  of  expense  connected  with  the 
running  of  the  plant  and  takes  into  account  all  renewals  and  changes  made. 
but  does  not  include  depreciation  of  property. 

GENERAL. 

From  a  large  number  of  experiments  made  on  the  oxidized  ores  the 
conclusions  reached  are  that  fine  crushing,  long  time  treatment,  and  a  large 
volume  of  low  strength  solution  give  the  best  results. 

Roasting  does  not  materially  improve  the  extraction,  neither  does  the 
use  of  oxidizing  agents  such  as  bromine  appear  to  help. 

Free  gold  has  only  .rarely  been  encountered  in  small  quantities  and 
amalgamation  tests  give  no  encouragement.  Concentration  tests  show  that 
there  is  very  little  concentratable  material  in  the  ore  and  the  concentrates 
obtained  are  not  of  sufficient  grade  to  treat  further  even  if  the  percentage 
of  extraction  would  justify  such  treatment. 

Chlorination  on  raw  ores  gives  very  low  results  while  on  roasted  ores 
no  better  results  are  obtained  than  by  cyaniding. 


Black  Hills  Mining  Meris  Association.  81 


Tests  made  on  the  blue  ores  have  given  absolutely  no  encouragement 
unless  first  roasted  dead  at  a  comparatively  fine  mesh  after  which  they 
yield  from  seventy  to  eighty  per  cent  extraction  by  either  cyaniding  or 
rhlorination. 

In  our  experiments  on  the  raw  treatment  of  blue  ores  we  have  been 
unable  to  get  gold  into  solution,  the  maximum  extraction  by  cyanide  treat- 
ment being  thirty  per  cent  with  even  lower  extractions  by  other  methods. 


82  Black  Hills  Mining  Men's  Association. 

CYANIDE   PRACTICE   AT   THE   IMPERIAL   MILL   AND   SOME 

COMPARISONS  OF    DRY  WITH  WET  CRUSHING 

IN  CYANIDE  SOLUTION. 

BY  JOHN  T.  MILLIKEN,  E.  M.,  SUPERINTENDENT  IMPERIAL  MILL. 
[Paper  read  before  Black  Hills  Mining  Men's  Association,  August,  1904.] 

The  object  of  this  paper  is  to  describe  briefly  the  reduction  of  ores 
by  the  "dry  fine  crushing"  process,  in  an  up-to-date  dry  crushing  mill, 
and  at  the  same  time  make  a  few  impartial  and  honest  comparisons  with 
an  up-to-date  and  modern  "fine  wet  crushing  mill." 

There  are  but  two  cyanide  mills  in  the  Black  Hills  reducing  ores  by 
the  dry  fine  crushing  process — the  Golden  Reward  Mining  Company's  mill, 
with  a  monthly  capacity  of  5,000  tons,  and  the  Imperial  Gold  Mining  & 
Milling  Company's  mill,  with  an  average  capacity  of  4,000  tons  per  month. 
The  excellent  results  attained  by  the  Golden  Reward  Company,  in  their 
dry  crushing  cyanide  mill  need  no  mentioning  here,  so  the  writer  will  confine 
himself  to  the  mill  of  the  Imperial  Gold  Mining  &  Milling  Company,  as  it 
is  a  more  modern  mill,  and  equipped  with  the  necessary  machinery  for 
economic  handling  of  the  ore. 

THE  ORE. 

The  ore  is  from  the  Potsdam,  extremely  hard,  tough,  close  grained, 
highly  siliceous  and  the  gold  minutely  disseminated.  Eighty  per  cent 
of  the  ore  as  it  comes  from  the  mine  is  fairly  well  oxidized.  The  remaining 
twenty  per  cent  is  what  is  known  as  the  blue  ore.  This  blue  ore  is  very 
refractory,  close  grained,  carries  from  four  to  five  per  cent  iron  pyrite, 
traces  of  arsenic,  as  arsenopyrite  and  antimony.  In  fact  it  is  this  blue  ore 
that  makes  it  difficult  to  recover  seventy-five  to  eighty  per  cent  from  the 
low  grade  gold  ores  of  the  Black  Hills,  but  as  the  blue  and  oxidized  ores 
are  mined  together,  it  is  absolutely  impossible  to  eliminate  all  the  unoxi- 
dized  ore. 

MILLING. 

The  Imperial  mill  is  a  flat  site  mill,  each  department  having  its  'Own 
building  independent  from  the  mill  proper.  This  form  of  construction 
affords  perfect  control  of  the  dust  and  confines  it  to  the  building  wherein 
it  is  produced;  which,  on  the  other  hand,  or  in  a  hill-side  mill,  where  all 
departments  are  practically  under  one  roof,  dust  produced  in  any  one  por- 
tion flies  through  and  permeates  the  whole  mill.  The  engine  room,  the 
leaching  and  precipitating,  department,  are  absolutely  separate  from  the 
fine  crushing  de'partment,  which  is  the  only  department  where  dust  is 
produced. 

The  mill  is  well  provided  with  railroad  spurs,  both  on  the  Burlington 
&  Missouri  River  and  Chicago  &  Northwestern  Railroads.  The  ore  is  re- 
ceived from  the  mines  in  bottom  dump  cars,  and  immediately  dumped 
into  railroad  bins,  and  is  drawn  directly  from  here  into  a  10x20  Blake 
orusher.  running  250  revolutions  per  minute,  and  is  here  reduced  to  rock 


Black  Hills  Mining  Men's  Association.  83 

varying  from  fine  sand  to  pieces  having  an  extreme  dimension  of  two  inches. 
The  discharge  from  the  crusher  feeds  directly  into  a  twelve-inch  bucket  eleva- 
tor, fourteen-inch  nine-ply  belt  speed  300  feet  per  minute.  This  elevator  dis- 
charges directly  into  a  3x6-foot  Hexagon  screen  revolving  fifteen  revolu- 
tions per  minute,  which  gives  a  sized  product  varying  from  fines  to  ore 
having  an  extreme  dimension  of  one  inch.  The  oversize  from  this  screen 
returns  to  a  pair  of  16x36  Davis  rolls,  speed  sixty  revolutions  per 
minute,  and  the  undersized  is  carried  by  .a  sixteen-inch  belt  conveyor  to 
storage  bins  having  a  combined  capacity  of  one  thousand  tons.  The  dis- 
charge from  this  16x36-inch  rolls  joins  the  feed  from  the  crusher  and  is 
again  elevated  to  the  sizing  screens,  so  nothing  goes  to  storage  bins  but 
carefully  sized  material. 

This  is  known  as  the  sampling  department,  or  preliminary  crushing. 
The  sample  is  cut  from  the  sized  ore  as  it  leaves  the  above  mentioned  screen, 
and  is  cut  out  with  a  Vezin  Automatic  Sampler.  This  sampler  cuts  out 
accurately  one-twenty-fifth  of  the  ore  which  is  spouted  to  steel  covered 
floor  provided  for  it,  and  is  here  finally  reduced  by  splitting  with  a  Jones 
sampler  to  a  definite  weight,  and  run  through  a  pair  of  12x12  sampling 
rolls,  cut  or  reduced  further  with  a  riffle,  thoroughly  dried,  and  finally 
ground  in  a  No.  2  sample  grinder  to  about  eighty  mesh,  thoroughly  mixed, 
cut  with  a  riffle  to  about  ten  ounces  and  bucked  through  120  mesh  screens, 
and  two  samples  made. 

This  amount  of  work  necessary  to  obtain  a  representative  sample  of 
a  particular  lot  of  ore,  may  seem  unnecessary  to  some,  but  the  value  to  a 
plant  of  trustworthy  sampling  far  exceeds  the  money  cost,  and  figures 
based  on  any  other  but  an  accurate  head  sample  are  very  misleading. 

FINE  CRUSHING. 

The  ore  from  the  above  mentioned  bins  is  now  fed  onto  a  twelve-inch 
belt  conveyor  by  an  automatic  fine  ore  feeder,  this  feeder  provides  a  steady 
and  unvarying  feed  to  the  rolls,  an  absolute  necessity  for  good  work.  The 
belt  conveyor  discharges  into  a  ten-inch  bucket  elevator  eleven-inch  seven- 
ply  belt,  speed  300  feet  per  minute,  which  discharges  directly  into  a  No.  2-4 
Tube  Argall  Dryer.  This  dryer  consists  of  four  fire  brick  lined  steel  tubes, 
nested  together  inside  of  two  tires,  and  provided  at  the  ends  with  heads 
which  serve  to  feed  and  receive  the  wet  ore,  and  to  discharge  the  dried  ore. 
These  tubes  are  twenty-five  inches  in  diameter  and  twenty-five  feet  long. 
This  dryer  has  given  excellent  satisfaction,  requiring  a  minimum  of  fuel, 
one  horse  power  for  revolving  under  full  load,  and  the  repairs  are  nominal. 
It  is  placed  on  a  slight  incline  three-fourths  of  an  inch  to  the  foot  and  makes 
two  revolutions  per  minute. 

The  temperature  maintained  in  this  dryer  at  the  Imperial,  is  close  to 
300  degrees  Fahrenheit,  this  temperature  dehydrates  the  ore  thoroughly, 
and  very  materially  increases  the  filtering  or  percolation  in  the  cyanide  vats. 
Figures  will  be  given  further  on  relative  to  fuel,  repairs  and  condition  of 
ore  after  drying. 


Black  Hills  Mining  Men  8  Association.  85 

The  dryer  discharges  directly  into  a  roller  chain  continuous  bucket 
elevator,  provided  with  twenty-five-inch  traction  wheels  for  head  and  boot 
pulleys,  and  has  a  speed  of  150  feet  per  minute. 

This  chain  elevator  discharges  directly  into  a  2£x6-foot  cylindrical 
screen,  revolving  fifteen  revolutions  per  minute,  and  covered  with  five  mesh 
No.  16  wire,  opening  .137  inches.  The  oversize  discharges  •  and  passes  to 
a  pair  of  16x36  Davis  rolls,  running  fifty-five  revolutions  per  minute, 
the  discharge  from  this  roll  joins  the  feed  from  the  dryer  and  is  again  elevated 
and  sized.  The  undersize  from  the  above  screen  passes  to  the  finishing 
rolls,  that  is,  one-half  of  the  feed  from  the  roughing  rolls  passes  to  one  of 
the  ten-inch  bucket  elevators,  twelve-inch  seven-ply  belt,  and  is  elevated 
and  discharges  into  two  cylindrical  revolving  screens  four  feet  in  diameter, 
eight  feet  long,  revolving  fifteen  times  per  minute,  and  covered  with  six- 
teen mesh  No.  21  steel  wire  cloth,  size  of  opening  .0305  (finished  pulp). 
This  system  gives  the  ore  from  the  roughing  roll  a  thorough  screening  before 
it  passes  to  the  finishing  rolls,  16x36  Davis  rolls,  running  seventy 
revolutions  per  minute.  This  is  one  unit.  These  screens  are  completely 
housed  in  with  steel  housing,  and  are  practically  dust  proof.  The  under- 
sized or  finished  pulp  passes  to  a  ten-inch  bucket  elevator,  twelve-inch 
seven-ply  belt,  and  is  immediately  elevated  to  finished  ore  bin.  The  over- 
size from  the  above  screen  discharges  directly  to  the  finishing  rolls,  recrushed 
and  joins  product  coming  from  roughing  roll,  and  is  elevated  again  to  finish- 
ing screens.  There  are  two  finishing  rolls,  each  receiving  one-half  of  the 
feed  from  roughing  roll,  each  finisher  having  two  screens  four  feet  in  diameter, 
eight  feet  long,  one  screen  on  each  side  of  the  ten-inch  bucket  elevator. 
This  close  sizing  from  crusher  onto  finishing  rolls  has  been  proven  absolutely 
necessary,  owing  to  the  extreme  hardness  of  the  ore,  but  the  rub  lies  in  the 
toughness  and  density  of  the  ore,  which  from  the  finishing  screens  since 
February  1st,  have  averaged  100.7  pounds  per  cubic  foot,  and  the  general 
average  for  twenty  months  has  been  ninety-eight  pounds  per  cubic  foot. 
Since  this  close  sizing  has  been  inaugurated,  all  the  rolls,  more  especially 
the  finishers,  have  been  running  quietly,  without  shock  or  undue  strain, 
and  has  cut  the  steel  shell  cost  from  eight  cents  per  ton  to  four  and  three- 
fourths  cents,  and  reduced  short  shut-downs  to  a  minimum. 

CYANIDE  TREATMENT. 

The  oi^e  from  finished  pulp  bin  is  fed  directly  on  to  a  nine-inch  screw 
conveyor,  eight  feet  long,  and  at  this  point  the  ore  is  sprayed  with  the  cya- 
nide solution  in  order  to  do  away  with  the  dust  in  the  leaching  room,  which 
it  does  very  effectually.  This  screw  conveyor  disharges  onto  a  fourteen- 
inch  belt  conveyor,  which  in  turn  discharges  onto  a  fourteen-inch  belt 
elevator,  fourteen-inch  nine-ply  belt,  speed  300  feet  per  minute.  The  dis- 
charge from  the  elevator  feeds  to  another  fourteen-inch  belt  conveyor, 
passing  over  the  leaching  vats,  and  from  this  conveyor  all  the  vats  are 
filled.  There  are  four  leaching  vats,  six  feet  deep,  thirty-five  feet  in  diameter 
and  built  of  three-sixteens-inch  steel,  and  when  filled  within  three 


Black  Hills  Mining  Men's  Association. 


inches  of  the  top,  hold  approximately  275  tons  of  ore.  In  filling  the  vats 
the  ore  is  always  charged  into  standardized  solution,  five  pounds  cyanide 
to  a  ton  of  water,  so  when  vat  is  filled  it  is  practically  saturated.  However, 
after  vats  are  filled  and  leveled  off,  the  surface  is  flooded  with  standard 
solution  and  charge  allowed  to  stand  until  perfectly  quiet,  or  thoroughly 
saturated.  Leaching  is  then  started  and  continuous  percolation  kept  up 
until  charge  is  washed.  Time  required  to  fill  a  vat  is  fifty  hours,  and  treat- 
ment will  average  eight  days.  The  amount  of  cyanide  solution  in  tons 
required  for  treatment,  taking  100  charges  as  an  average,  is  as  follows: 

65  tons  5  pounds  solution  for  saturation. 

70  tons  3i  to  4  pounds  solution  returned  from  strong  sump. 

20  tons  of  1\  to  3  pounds  solution  returned  from  weak  sump. 

50  to  55  tons  of  wash  water. 

Practically  six-tenths  of  a  ton  of  solution  to  each  ton  of  ore  treated. 
Larger  amounts  of  the  solution  have  been  often  used,  as  much  as  200  tons 
of  weak  and  strong  have  been  returned  to  a  vat  without  any  apparent 
increase  in  extraction,  and  amounts  as  low  as  600  pounds  of  solution  to 
one  ton  of  ore  have  given  the  same  tailings  as  when  the  normal  1,200  pounds 
per  ton  of  ore  has  been  passed  through  the  charge.  The  maximum  value 
of  the  effluent  solution  is  reached  in  about  fifty  to  sixty  hours  after  the  vat 
has  begun  leaching,  and  has  often  run  as  high  as  two  ounces  per  ton,  and  a 
very  fair  average  for  all  charges  would  be  about  $30.00,  or  one  and  one-half 
ounces  per  ton.  The  dissolution  seems  to  take  place  very  rapidly,  and  when 
the  above  value  is  reached  it  begins  to  decrease  very  rapidly,  but  gradually. 
All  the  solutions  coming  from  leaching  vats,  including  the  wash  water,  are 
passed  through  zinc  boxes. 

The  vats  are  provided  with  the  usual  filter  grating,  covered  with  coco 
matting  and  eight-ounce  duck,  and  have  five  eight-inch  diameter  Argull 
sluicing  gates,  one  in  the  center,  and  one  in  each  quadrant,  and  are  sluiced 
out  in  the  usual  manner  with  hydraulic  pressure. 

PRECIPITATION. 

In  the  precipitation  department  there  are  two  gold  storage  tanks  four 
feet  deep  and  twenty  feet  in  diameter,  built  of  three-sixteens-inch'  steel. 
These  tanks  are  for  the  effluent  and  weak  solution.  There  are  two  sumps 
immediately  under  the  zinc  boxes,  and  are  the  same  size  as  the  gold  storage. 
There  are  two  double  compartment  zinc  boxes,  fourteen  compartments 
two  feet  square  and  two  feet  deep  to  each  box,  or  twenty-eight  in  all.  These 
compartments  hold  when  closely  packed  fifty-five  pounds  lathe  turned  zinc. 

The  present  zinc  area  required  for  precipitating  the  values  from  130 
tons  of  ore  per  day  is  104  cubic  feet,  containing  800  to  1,100  pounds  zinc 
shavings,  that  is  just  before  a  clean  up  takes  place,  the  boxes  will  contain 
1,100  pounds  zinc  shavings,  the  first  two  compartments  will  contain  practi- 
cally 150  pounds  each,  and  it  may  sound  incredible  but  it  is  a  fact  that  fully 
95.5  per  cent  of  the  precipitation  takes  place  in  the  first  two  boxes  on  the 
strong  side. 


Black  Hills  Mining  Men's  Association.  87 

There  are  only  three  boxes  of  the  fourteen  on  the  weak  side  used, 
three  of  them  being  sufficient  to  keep  sump  thoroughly  clean.  The  solutions 
are  standardized  by  pumping  from  sumps  in  to  two  standardized  tanks, 
sixteen  feet  deep  and  fourteen  feet  in  diameter,  and  are  also  built  of  three- 
sixteenths-inch  steel. 

EXTRACTION. 

In  the  mill  there  is  no  separation  made,  of  the  sands  and  slimes.  The 
ore  is  treated  as  it  comes  from  the  rolls,  sands  and  slimes  together,  a  system 
which  permits  of  the  closest  watch  possible  on  extraction.  The  amount  of 
gold  solution  passing  through  zinc  boxes  is  readily  measured,  constantly 
sampled  and  checked  with  the  total  solution,  returned  from  sumps,  and 
with  the  drip  samples  taken  on  each  tank  continuously  during  its  entire 
leaching  period,  including  .washing.  This  extraction  compared  with  the 
extraction  figured  on  the  difference  between  control  and  tailing  assays,  is 
about  1.4  per  cent  higher.  The  actual  bullion  return  checks  with  the  solu- 
tion extraction  within  1.5  per  cent,  the  actual  bullion  return  being  1.5  per 
cent  higher.  The  actual  bullion  return  since  mill  was  started  is  78.2  per 
cent. 

The  operating  cost  per  ton  of  ore  treated,  for  the  last  running  twelve 
months,  based  on  a  daily  tonnage  of  100  tons  per  day  is  as  follows: 

LABOR  AND  SUPPLIES. 

Per  ton 

Labor $0.580 

Fuel  for  power 0 . 255 

Fuel  for  drying 0 . 110 

Lubricants ,  . '. 0 . 051 

Roll  steel 0 . 057 

Equipment  supplies 0 . 045 

Cyanide 0 . 120 

Zinc 0 . 070 

Melting  supplies 0 . 014 

Assay  supplies 0.015 

Miscellaneous  supplies 0 . 040 

Insurance 0 . 030 

$1.387 

The  tonnage  now  being  maintained  is  130  tons  per  day  of  twenty-four 
hours.  And  when  contemplated  improvements  are  perfected,  the  operating 
cost  will  be  further  reduced. 

THE  CLEAN  UP. 

The  usual  sulphuric  acid  method  of  cleaning  up  is  used.  And  owing 
to  the  small  amount  of  sol  passed  through  boxes  and  its  freedom  from 
slimes,  the  precipitates  are  high  grade  and  in  an  excellent  state  for  dissolu- 
tion with  the  acid.  Considerable  coarse,  or  zinc  that  has  begun  to  decom- 
pose, is  also  removed,  with  the  fine  precipitates. 

The  precipitates  are  washed  free  from  cyanide  solution  by  being  dis- 
charged directly  from  the  boxes  into  a  vacuum  filter  two  feet  deep  and  four 


Black  Hilh  Mining  Men's  Association. 


feet  in  diameter,  provided  with  a  filter  bottom  of  coco  matting,  ten-ounce 
duck,  and  this  covered  with  a  heavy  quality  of  lawnsdale  muslin,  which  reaches 
up  over  the  top  of  the  filter  proper.  The  precipitates  are  removed  from 
here  to  a  steel  lead  lined  tank  two  and  a  half  feet  deep,  five  feet  in  diameter. 
Hot  water  is  now  added  so  as  to  give  a  final  acid  dilution  of  one  in  six, 
the  precipitates  having  been  weighed  as  they  were  transferred  to  the  dis- 
solving tank.  Acid  is  now  added  gradually  until  it  reaches  the  above  ratio, 
and  when  this  has  been  reached  the  zinc  precipitates  is  well  dissolved,  no 
coarse  zinc  being  present. 

The  dissolving  tank  is  now  covered  and  the  contents  given  a  vigorous 
boil  for  one  hour.  The  boiling  is  now  stopped,  the  sides  of  the  tank  now 
carefully  washed  down  with  a  small  stream  of  hot  water,  and  the  contents 
run  out  into  another  vacuum  filter,  the  same  size  as  the  one  described,  and 
the  liquid  drawn  off  slowly  but  steadily,  until  dry,  three  hot  water  washings 
are  now  given,  precipitates  being  carefully  stirred  each  time  until  they  are 
all  in  suspension.  The  precipitates  are  then  dried  with  the  vacuum  until 
they  begin  to  crack.  They  are  now  removed  and  placed  in  sheet  steel  pans, 
(the  bottom  of  these  pans  are  first  covered  with  paper,  this  keeps  the  slimes 
from  sticking  to  pans),  and  dried  slowly  in  cast  iron  muffles,  the  flame 
passing  over  the  top,  390  pounds  of  precipitates  as  they  come  from  the  boxes 
have  been  cut  down,  thoroughly  washed  and  placed  in  the  dryer  in  eight 
hours,  care  and  cleanliness  not  being  sacrificed  for  speed. 

The  precipitates  after  drying  are  fluxed  with  twenty-two  per  cent 
borax  glass,  twenty  per  cent  soda,  fifteen  per  cent  silica,  covered  with 
crude  borax  and  fused  in  wind  furnaces.  No  additions  are  made  during 
fusion. 

The  bullion  has  averaged  for  the  past  six  months  935.7  per  cent,  fine 
metal. 

Average  time  spent  on  clean  up  eighteen  hours.     The  slimes  are  dried 
during  the  night,  melting  started  in  the  morning,  two  men  carry  out  the 
work.     Average  cost  per  ounce  of  bullion  recovered  7.1  cents.     The  bullion 
for  the  past  four  months  has  averaged  as  follows: 
504.5  per  cent  silver 
431.2  per  cent  gold 

935.7 
The  slags,  pot  scapings  and  mattes  are  run  to  base  bullion  with  litharge. 

COMPARISONS. 

The  following  are  a  few  comparisons  with  the  fine  wet  crushing  plants, 
and  some  of  the  so-called  bad  features  of  the  dry  crushing  discussed. 

One  of  the  drawbacks  to  the  fine  dry  crushing  mill  is  the  dust  It  is 
indeed  the  principal  one,  but,  however,  is  very  much  magnified  as  to  its 
numerous  drawbacks  by  popular  talk.  The  dust  is  hard  on  the  pulmonary 
organs  of  the  workmen,  and  disagreeable  to  work  in,  and  hard  on  bearings 
and  machinery.  But  with  the  present  improvements  for  handling  dust, 
and  *the  mill  designed  with  a  view  to  keeping  the  dust  confined  to  that 


90  Black  Hills  Mining  Men's  Association. 

particular  department  where  it  is  produced,  a  fine  dry  crushing  plant  will 
not  be  a  bad  place  to  work,  and  there  will  be  no  difficulty  in  keeping  men. 

Another  point  put  up  against  the  dust  or  fine  dj*y  crushing  is  the  loss  in 
values  from  the  escaping  dust.  There  is  a  loss  in  values  by  escaping  dust, 
so  is  there  a  loss  also  in  dissolved  gold  in  the  wet  crushing  process,  and  a 
loss  that  far  exceeds  anything  the  writer  has  ever  seen  in  good  dry 
crushing  plants. 

I  will  describe  briefly  the  method  of  handling  the  dust  produced  at 
the  Imperial  mill,  and  give  a  few  figures  on  the  same. 

The  only  dusty  and  dust-producing  portion  of  the  mill  is  the  fine  roll 
room.  All  the  screens  are  steel  housed,  elevators  are  thoroughly  housed, 
and  heads  are  covered  with  ten-ounce  duck.  All  these  housings  and  places 
where  dust  is  generated  are  connected  up  with  four-inch  galvanized  iron 
pipe,  all  these  pipes  are  connected  to  one  central  head  attached  to  two 
thirty-five-inch  exhaust  fans,  that  draw  and  collect  the  dust  and  blow  it 
into  two  No.  39  Prinz  Rau  dust  collectors,  which  accumulate  the  dust  and 
discharge  it  automatically,  into  small  boxes  attached  to  wheel  barrows, 
and  it  is  mixed  with  the  finished  pulp  and  treated  with  it.  The  amount  of 
dust  collected  by  these  two  dust  collectors  from  130  tons  of  ore  every  twenty- 
four  hours  is  3,222  pounds,  97.2  per  cent  of  it  passes  through  a  150  mesh 
laboratory  screen,  assays  $10.65  per  ton  and  was  drawn  from  ore  running 
$8.00  per  ton.  This  dust  weighs  fortj^-nine  and  a  half  pounds  per  cubic 
foot.  The  original  ore  weighs  100.7  pounds  per  cubic  foot. 

The  dust  produced  by  the  dryer  is  caught  in  a  dust  flue  connected  with 
it.  This  dust  flue  is  4x5  feet  high  in  the  clear,  and  is  107  feet  long.  The 
dust  produced  by  dryer  amounts  to  three-tenths  of  one  per  cent,  and  assays 
twenty-five  per  cent  less  than  the  original  heads,  or  the  average  of  the  dust 
since  mill  started  $5.00  per  ton,  a  very  unusual  state  of  affairs  for  dust 
values,  for  as  a  rule  the  dust  will  run  from  one  and  one-half  to  three  times 
the  value  of  the  original  ore. 

The  dust  that  accumulates  throughout  the  mill  hardly  ever  exceeds 
the  .value  of  the  ore. 

The  dust  that  escapes  from  the  buildings  is  lost.  But  inferring  from 
dust  saved  by  dust  collector,  tank  weights  and  bullion  recovery,  based  on 
accurately  sampled  ore,  it  is  undoubtedly  below  one-half  of  one  per  cent. 

Comparing  this  dust  proposition  with  the  slimes  loss  in  the  wet  crush- 
ing mills,  there  seems  to  be  food  for  thought.  I  will  base  all  comparison 
on  results  and  information  from  Mr.  Gross,  Superintendent  of  the  Penobscot 
mill,  as  the  mill  is  one  of  the  most  up-to-date  and  modern  wet  crushing 
mills  in  the  Black  Hills,  and  great  care  being  given  to  arrive  at  and  determine 
accurate  results. 

Percentage  of  slimes  produced  in  crushing  wet  with  stamps  at  the 
Penobscot  mill  is  51.8  per  cent  of  the  total  ore  crushed.  These  slimes  are 
conducted  to  tanks  with  thirteen  tons  of  cyanide  solution  to  each  ton  of 
dry  slimes,  and  are  here  agitated  and  washed  by  decantation.  They  are 
given  three  dilutions  with  weak  cyanide  solution  decanted  each  time  but 
with  several  hours  agitation  with  each  decantation.  They  are  finally  given 


Black  Hills  Mining  Men's  Association.  91 


one  water  wash,  and  then  sluiced  out,  containing  46.7  per  cent  moisture, 
and  46.1  cents  per  ton  dissolved  gold,,  the  amount  of  undissolved  gold  I 
have  no  figure  on. 

Forty-six  and  one-tenth  cents  per  ton  dissolved  gold  escaping  would 
be  at  the  rate  of  twenty-four  cents,  figuring  51.8  per  cent  of  the  ore  treated 
as  slimes,  or  three  per  cent  on  an  ore  running  $8.00,  a  very  high  dust  loss 
indeed.  The  Dakota  M.  and  M.  Co.'s  loss  is  also  three  per  cent. 

Another  point  might  be  mentioned  regarding  moisture — they  say,  why 
dry  your  ore,  it  will  take  up  and  use  so  much  of  your  water.  Well,  it  does 
take  out  with  it  some  water,  an  average  on  100  vats  shows  the  pulp  contains 
on  going  out  12.0  per  cent  moisture.  This  is  several  per  cent  higher  than 
necessary  if  water  were  short.  However,  this  is  considerably  less  than  46.7 
per  cent  moisture. 

Drying  the  ore  is  one  expense  the  wet  crushing  mills  avoid, 
but  the  disadvantage  of  having  to  dry  your  ore  is  more  than  offset  when  it 
comes  to  leaching  the  pulp.  It  is  a  well  known  fact  that  when  ore  is  heated 
to  a  temperature  of  300  degrees  Fahrenheit,  it  is  dehydrated  and  the  leaching 
accelerated  five  or  six  fold.  At  the  Imperial  mill  tests  have  verified  this. 

The  following  pulp  will  leach  at  the  rate  of  thirty-five  tons  per  twenty- 
four  hours,  when  thoroughly  dried — vat  six  feet  deep,  containing  five  feet 
seven  inches  of  ore. 

Per  cent 

Remaining  on    20  mesh.  .  . 2.5 

Remaining  on    30  mesh 11.0 

Remaining  on    40  mesh 10.0 

Remaining  on    60  mesh 18.0 

Remaining  on    80  mesh 9.0 

Remaining  on  100  mesh 4.0 

Passing  100  mesh 45 . 5 

Twenty-one  and  one-half  per  cent  of  this  45.5  per  cent  will  pass  a  150 
mesh  screen.     These  screens  are  the  usual  brass  wire  screens  of  the  laboratory. 
Cost  of  drying  ore  at  the  Imperial  mill  and  maintaining  dryer  in  good 
repair,  is: 

Per  ton 

Fuel $0 . 110 

Repairs , 0 . 010 

Labor 0 .0175 

Power. 0 . 0030 

$0.1405 
Drying  at  the  Golden  Re\vard  Mining  Company  mill  costs: 

Per  ton 

Fuel .$0.0700 

Labor 0 . 0330 

Repairs 0 . 0100 

Power .    0 . 0030 


$0.1160 

Another  point  in  favor  of  drying,  and  a  good  one,  is  in  place  of  the 
cyanide  solution  coming  in  contact  with  frozen  ore,  which  is  the  case  in  a 
wet  crushing  plant  during  the  winter  months,  it  comes  in  contact  with 


92  Black  Hills  Mining  Men's  Association. 

warm  ore.     This  insures  an  even    temperature    throughout    the  year,  and 
consequently  a  uniform  extraction. 

ELEVATORS. 

Elevators  and  the  power  to  elevate  the  ore  so  much  is  another  thing 
the  wet  crushing  m,ills  claim  they  are  free  of.  They  are  free  of  elevators  but 
not  free  from  the  cost  of  elevating.  In  almost  all  ore  milling  operations 
one  of  the  most  useful  and  necessary,  and  at  the  same  time  most  objurgated 
pieces  of  apparatus  is  the  belt  elevator.  Yet,  if  a  belt  elevator  is  properly 
designed  it  should  not  give  any  more  trouble  than  more  complicated  ma- 
chinery, which  is  exposed  to  equally  hard  conditions  of  service. 

All  the  elevators  in  the  Imperial  mill  are  provided  with  the  best  rubber 
belts  and  malleable  iron  buckets,  have  a  speed  of  300  feet  per  minute,  strict 
attention  being  paid  to  the  feed  and  discharge. 

There  are  six  rubber  belt  elevators  in  the  Imperial  mill  and  one  con- 
tinuous bucket  chain  elevator. 

No.  1  elevator 42  feet  center  to  center. 

'-.        No.  2  elevator 22  feet  center  to  center. 

No.  3  elevator 26  feet  center  to  center. 

Nos.  4  and  5  elevators 38  feet  center  to  center. 

No.  6  elevator 50  feet  center  to  center. 

No.  7  elevator 35  feet  center  to  center. 

Elevators  Nos.  4  and  5  are  for  the  finishing  rolls. 

No.  1  elevator  handles  130  tons  in  12  hours.     • 

No.  2  elevator  handles  130  tons  in  24  hours. 

No.  3  elevator  handles  130  tons  in  24  hours. 

Nos.  4  and  5  elevators  handle  65  tons  each  in  24  hours. 

No.  6  elevator  handles  130  tons  in  24  hours. 

No.  7  elevator  handles  275  tons  in  52  hours. 

The  above  seven  elevators  require  1.90  theoretical  horse  power  and 
allowing  an  equal  amount  for  friction,  the  total  is  3.8  horse  power.  There 
are  also  four  belt  conveyors,  a  liberal  allowance  for  power  in  this  case  is 
four  horse  power,  making  a  total  power  for  elevating  and  conveying  ore 
7.6  horse  power. 

The  cost  of  operating  is:  .     . 

Per  ton 

Power $0 . 016 

Repairs 0 . 018 

$0.034 
or  three  and  four-tenths  cents  per  ton  of  ore  treated. 

The  following  are  Mr.  Gross'  figures  on  elevating  at  the  Penobscot  mill: 

Running  and  maintaining  of  two  Fiernier  sand  pumps  for  the  past 
year.  Lift  from  battery  discharge  to  classifiers  20.5  feet  36,200  tons  pulp 
and  1,810,000  tons  solution. 

Power 2.45  cents  per  ton  of  ore. 

Supplies 0 . 03  cents  per  ton  of  ore. 

2 . 48  cents  per  ton  of  ore. 


Black  Hills  Mining  Men's  Association.  93 

Repairs  on  two  Fiernier  Sand  pumps  for  the  last  year: 

Material 0.21  cents  per  ton. 

Labor 0 . 06  cents  per  ton. 

0 . 27  cents  per  ton. 

Or  2.75  cents  per  ton  of  ore  for  elevating  from  battery  discharge  to 
cone  classifiers. 

The  cost  of  handling  slime  during  washing  and  decantation  is: 
Repairs  on  two  No.  4  centrifugal  pumps  for  one  year,  handling  220,000 
tons  of  dry  slimes,  with  approximately  1,500,000  tons  solution,  (this  in- 
cludes transferring  and  agitation)  lift  of  pump  twenty-nine  feet  under 
average  head  of  eighteen  feet,  average  per  lift  eleven  feet,  only  repairs  being 
a  new  shaft  for  each  pump. 

Material 0.04  cents  per  ton  of  ore  in  mill. 

Labor 0 . 05  cents  per  ton  of  ore  in  mill. 

0.09  or  0.015  cents  per  ton  of  ore  handled. 

Power 2.02  cents  per  ton  of  ore  in  mill. 

Supplies 0 . 09  cents  per  ton  of  ore  in  mill. 

2;  11  or  0.35  cents  per  ton  of  slimes  handled. 

The  above  figures  based  on  the  ore  handled  in  the  mill  show  a  cost  of 
four  and  three  quarters  cents  per  ton  of  ore  handled. 

There  is  also  in  the  neighborhood  of  1,100  tons  of  solution  per  day 
pumped  from  the  sump  to  battery  storage  tank,  with  an  average  lift  of  eighty- 
five  feet,  a  reasonable  allowance  for  this  would  be  about  six  horse  power, 
or  the  cost  would  be  approximately  for  power,  labor  and  repairs,  about 
two  cents  per  ton,  or  a  total  of  six  and  three-fourths  cents  per  ton  for  ele- 
vation of  material,  as  against  $0.034  per  ton  in  the  Imperial  mill.  The 
Dakota  M.  and  M.  Co.'s  cost  for  elevating  is  .06.85  cents  per  ton. 

The  following  are  figures  given  by  the  Golden  Reward  Mining  Company, 
and  are  based  on  a  tonnage  of  101,682  tons  in  a  dry  crushing  plant: 

Per  ton 

Roll  steel $0 . 0.426 

Bab  belt  metal 0 . 0182 

Elevator  buckets 0 . 0016 

Elevator  belts 0 .0044 

$0.0668 
Or  6.68  per  ton. 

The  Golden  Reward  mill  has  but  four  elevators  and  no  conveyor. 

The  cost  of  steel  for  crushing  seems  to  be  very  much  the  same  thing 
for  the  wet  and  dry  plants. 

Comparison  on  consumption  of  chemicals,  figures  based  on  100  tons 
per  day  in  each  mill,  the  ores  in  each  case  being  very  similar  as  to  general 
character  and  value. 


94:  Black  Hills  Mining  Men's  Association. 

PENOBSCOT  WET  CRUSHING  PLANT. 

Average  strength  solution,  two  pounds;  cyanide  chemical  loss,  .98 
pounds;  cyanide  mechanical  loss,  .49  pounds;  pounds  of  zinc  in  contact, 
1,800  to  2,000  pounds,;  zinc  consumption  1.33  pounds. 

Total  cyanide  consumed  1.47  pounds  per  ton.  Tons  of  solution  passed 
through  zinc  per  ton  of  ore  4.65  tons. 

IMPERIAL  DRY  CRUSHING  PLANT. 

Average  strength  solution,  4.5  pounds;  chemical  and  mechanical  loss, 
cyanide,  .50  pounds;  pounds  zinc  in  contact,  800  to  1,200  pounds;  zinc 
consumption,  .70  pounds. 

Total  cyanide  consumed  .5  pounds  per  ton. 

Tons  of  solution  passed  through  zinc  per  ton  of  ore  .8  of  a  ton  including 
wash  water. 

The  average  amount  of  solution  passed  through  the  sands  or  coarse 
portion  of  the  ore  in  the  wet  crushing  plants  is  practically  ten  tons  to  every 
ton  of  ore.  This  is  due  principally  to  the  fact  that  it  is  absolutely  necessary 
to  keep  the  strength  of  working  solution  as  low  in  value  and  cyanide  as 
possible.  A  good  average  for  working  strength  in  cyanide  is  one  and  one- 
half  pounds  of  cyanide  to  the  ton  of  water,  such  strong  solutions  as  are 
used  in  the  dry  crushing  plants  are  prohibitive,  owing  to  the  large  mechan- 
ical losses  it  would  entail.  On  the  other  hand  the  value  of  the  solution 
coming  from  the  batteries  must  be  kept  down  as  low  as  possible,  otherwise 
the  loss  in  dissolved  gold  escaping  with  the  slimes  would  be  ruinous.. 

CONCLUSION. 

In  construction  the  wet  crushing  mill  is  much  the  simpler,  having  fewer 
pulleys,  belts,  generally  only  one  elevator,  and  no  screens  except  the  bat- 
tery screens. 

The  cost  of  construction  per  ton  of  ore,  will  be  practically  the  same  in 
mills  designed  to  treat  similar  ores. 

The-  wet  crushing  plants  are  more  cleanly  and  easily  kept  so.  On 
the  other  hand,  in  the  scope  or  elasticity  of  the  processes,  the  wet  crush- 
ing is  limited  in  many  ways.  First,  on  an  ore  running  high  in  values  and 
producing  a  very  large  percentage  of  slimes,  and  where  these  slimes  would 
carry  values  exceeding  the  original  or  heads  by  150  to  200  per  cent,  not  an 
unusual  condition  of  affairs.  One  very  unusual  characteristic  of  gold  ores, 
and  one  that  makes  the  low  grade  gold  ores  of  the  Black  Hills  particularly  appli- 
cable to  wet  crushing,  is  the  fact  that  the  slimes  carry  less  values  than  the 
sands  or  ore  from  which  they  were  separated.  Second,  On  ninety-five  per 
cent  of  the  low  grade  sulphide  ore  requiring  roasting,  the  Black  Hills  ore 
for  example,  the  blue  or  unoxidized  ore,  is  developing  very  rapidly,  and  in 
no  distant  time  the  mills  will  have  to  resort  to  roasting  and  cyaniding,  and 
all  the  ores  the  writer  has  experimented  on  will  have  to  be  crushed  to  at 
least  twelve  mesh,  and  sixteen  and  twenty  mesh  have  given  the  better  results. 


Black  Hills  Mining  Men's  Association.  95 

A  representative  sample  from  the  McGovern  property,  gave  the  follow- 
ing results,  on  roasting  at  different  meshes. 

Sulphur  contents  of  sample,  2.68  per  cent  S. 
Gold  contents  of  sample,  $10.80. 

These  samples  were  roasted  in  the  muffle  furnace,  and  the  temperature 
kept  as  near  as  possible  to  the  usual  temperature  maintained  for  low  sulphur 
ores.  That  is  from  500  degrees  Fahrenheit  to  1,500  degrees  Fahrenheit, 
the  finishing  heat. 

S.  contents          S.  contents 

before  after  Extraction 

Samples  were  crushed  to —  roasting  roasting  per  cent 

per  cent  per  cent 

Six  mesh  No.  16  wire, 

Size  of  opening  0.102 2.68  .972  14.2 

Eight  mesh  No.  16  wire, 

Size  of  opening  .060 2.68  .611  19.75 

Ten  mesh  No.  17  wire, 

Size  of  opening  .042 2 . 68  .220  52 . 1 

Twelve  mesh  No.  18  wire, 

Size  of  opening  .034 2.68  .161  66.8 

Sixteen  mesh  No.  20  wire 

Size  of  opening  .0275 2 . 68  .100  77 . 9 

Twenty  mesh  No.  23  wire 

Size  of  opening  .023 .    2.68  .071  83.7 

The  time  and  strength  of  solution  was  the  same  in  each  case.  A  six 
pound  solution  was  used.  Cyanide  consumption  decreased  as  extraction 
increased,  owing  to  imperfect  roast.  The  extraction  on  the  sixteen  and 
twenty  mesh  product  took  place  extremely  rapid,  and  cyanide  consumption 
was  .83  of  a  pound.  The  pulp  leached  beautifully  and  the  leaching  was 
increased  about  eight  times  over  the  leaching  in  the  raw  state. 

Roasting  test  on  the  unoxidized  ores  from  the  Imperial  property  in 
Blacktail,  and  the  Bertha  property  in  Ruby  Basin,  all  show  good  extraction. 

Cynaide  roasting  tests  were  made  on  the  blue  ore  of  the  Portland 
Company  on  Bald  Mountain,  and  it  proves  to  be  an  excellent  roasting 
proposition. 

The  above  tests  point  very  strongly  to  fine  dry  crushing  and  roasting. 
The  Imperial  is  designed  with  a  view  to  roasting  their  unoxidized  ores, 
and  will  be  put  into  commission  at  no  distant  date. 

The  urtoxidized  ores  of  the  Hills,  when  crushed  to  about  twenty  mesh, 
will  yield  on  an  average  from  twenty-five  to  thirty  per  cent  of  their  values. 
A  good  average  value  for  the  blue  ores  of  the  Black  Hills  is  about  $11.00, 
which  when  treated  raw  will  yield  practically  $2.50  or  $3.00  per  ton,  but 
on  the  other  hand  if  properly  roasted  will  yield  at  least  $9.50  per  ton. 

This  roasting,  if  done  in  a  thoroughly  modern,  well-designed  plant, 
equipped  with  one  of  the  first  class  straight  line  furnaces,  and  proper  skill 
applied,  can  be  done  safely  for  the  following  figures,  based  on.  a  tonnage 
of.  100  tons  per  day. 


96  Black  Hills  Mining  Men's  Association. 

Per  ton 

Fuel $0.550 

Labor 0.065 

Repairs 0 . 100 

Power 0.010 

$0.725 

Fuel  is  figured  on  Sheridan  coal  at  $3.50  per  ton  at  the  mill,  and  the 
labor  item  is  for  one  man  on  each  shift  watching  and  firing  furnace.  It 
is  safe  to  say  that  75  cents  would  be  an  outside  figure  for  roasting  the  ore. 

The  general  conclusion  is,  that  a  modern  and  well  designed  dry  crush- 
ing plant  will  treat  the  same  ores  that  a  wet  crushing  plant  will,  and  a 
greater  variety  of  them,  and  do  it  cheaper  and  extract  a  larger  percentage 
of  the  values. 


Black  Hills  Mining  Men's  Association.  97 

CYANIDE  PRACTICE  IN  THE  BLACK  HILLS. 

BY  JOHN  RANDALL,  SUPERINTENDENT  OF  THE  LEXINGTON  HILL  MINE. 
[Paper  read  before  Black  Hills  Mining  Men's  Association,  June  19th,  1902.] 

MR.  CHAIRMAN  AND  GENTLEMEN: 

The  difficulties  which  ordinarilly  beset  the  cyanide  man  make  his  work 
somewhat  alluring  when  we  remember  that  leaving  out  the  man  who  is 
always  looking  for  trouble,  the  human  race  is  generally  happiest  when 
it  has  some  difficulties  to  encounter.  To  begin  with,  the  ore  of  good  value 
usually  goes  to  the  smelter  or  is  shipped  to  distant  parts  to  undergo  highly 
refined  and  expensive  processes  of  treatment  whereby  is  recovered  nearly 
or  quite  ninety-five  per  cent  of  its  value.  The  waste  from  this  shipping 
ore  is  often  denominated  cyaniding  ore.  The  cyanide  man  must  be  content 
with  treating  mud  and  dirt  and  leaves  and  roots  and  sods,  sparingly  mixed 
with  rock,  and  he  must  get  his  customary  extraction  of  104  per  cent.,  more 
or  less,  if  he  would  satisfy  the  demands  generally  coming  from  the  office 
for  bullion. 

The  definition  of  ore  is  a  rather  elastic  one.  For  the  purpose  of  the 
mill  man  a  gold  ore  may  be  defined — any  material  containing  enough  gold 
to  be  milled  at  a  good,  round  profit,  but  the  more  widely  accepted  defini- 
tion is  far  more  comprehensive,  and  includes  anything  from  sea  water  to 
mine  waste  or  other  waste  material  probably  including  the  discarded  cor- 
sets, old  shoes  and  superannuated  cats  in  the  back  yard  of  the  next  lot, 
and  which  only  a  portion  of  the  year  is  hidden  by  a  charitable  mantle  of 
snow  from  mortal  eye  and  metallurgical  investigation^  But  seriously,  the 
low  grade  ores  of  the  Black  Hills  have  stimulated  improvement  which 
cannot  fail  to  be  of  incalculable  benefit  to  the  district  and  to  the  world 
at  large. 

Some  tribes  of  Eskimos  require  every  male  child  at  a  certain  age  to 
pass  through  the  ordeal  of  being  tied  into  his  boat  and  thrown  into  the 
sea.  If  he  rights  his  craft  and  comes  out  he  is  regarded  as  being  able  to 
make  his  way  in  a  region  where  the  conditions  of  bare  existence  are  ex- 
tremely severe,  but  if  he  drowns  it  is  believed  he  is  better  thus  out  of  the 
way.  Now  the  cyanide  man  who  escapes  the  righteous  indignation  of  the 
manager  who  has  an  insatiable  desire  for  bullion,  or  the  mill  man  who  does 
not  die  a  merited  death  in  the  attempt  to  discover  gold  in  mine  waste,  is 
by  low  grade  ore  conditions  fprced  into  a  position  for  improving  the  state 
of  the  art  wherever  possible,  and  as  might  be  expected,  marked  improve- 
ments have  been  made  right  here  among  us  and  along  all  the  various  im- 
portant lines  of  cyanide  work. 

This  mention  of  "merited  death"  may  require  explanation.  There 
will  be  millions  of  tons  of  good  low  grade  ore  left  in  these  Hills  after  the 
present  generation  has  passed  away,  and  no  penalty  or  punishment  is  too 
severe  for  the  man  who  wastes  his  time  on  material  too  low  in  value  to 
yield  a  good,  liberal  profit  above  the  general  expenses  of  a  company  and 


98  Black  Hills  Mining  Meris  Association. 

depreciation  of  plant,  besides  the  usual  items  charged  up  to  cost  of  mining 
and  milling. 

But  this  paper  will  be  confined  as  nearly  as  possible  to  a  single  phase 
of  the  subject,  namely,  crushing  in  solution,  and  separate  treatment  of 
sands  and  slimes,  as  it  seems  to  the  writer  that  herein  is  the  most  favor- 
able field  for  advancement  under  the  particular  conditions  of  this  locality. 

When  we  recollect  how  often  we  are  obliged  to  go  back  to  first  princi- 
ples, even  in  these  days  of  marvelous  advancement,  and  note  how  really 
little  there  is  new  under  the  sun,  we  are  not  surprised  that  the  old,  noisy 
stamp  battery  is  taking  its  place  as  a  potent  factor  in  this  work  with  its 
freedom  from  complicated  details  and  its  ability  to  handle  anything  that 
comes  from  upon,  in  or  under  the  earth,  provided  it  is  fed  enough  hard 
rock  to  keep  the  shoes  from  pounding  iron,  at  least  a  part  of  the  time. 
Crushing  in  solution  has  come  to  stay  although  the  first  attempts  here  in 
that  direction,  like  all  new  things  were  not  fully  appreciated. 

In  the  middle  of  the  summer  of  1899,  a  man  began  fitting  up  a  little 
old  tumble-down  stamp  mill  in  Deadwood  gulch  for  the  purpose  of  stamp- 
ing ore  in  cyanide  solution.  He  was  not  altogether  a  brilliant  man,  but 
a  hard  and  conscientious  worker,  a  man  of  infinite  patience,  and  he  had 
an  idea.  He  was  financially  backed  by  a  few  men  of  slender  means  who 
had  a  large  amount  of  ore  too  low  in  value  to  be  treated  by  any  process 
yet  practiced  in  this  region.  People  laughed  at  the  attempt  to  settle  and 
circulate  enough  solution  in  a  mill  to  supply  stamp  batteries.  They  were 
told  that  the  experiment  was  being  proven  an  undoubted  success  in  New 
Zealand,  it  having  been  introduced  there  about  the  beginning  of  that  year. 
Most  people  are  too  busy  to  keep  well  posted  in  geography,  but  we  all  know 
that  New  Zealand  is  Somewhere  south  of  the  equator,  and  the  minds  of  some 
no  doubt  reverted  to  the  picture  that  long  ago  greeted  them  from  the 
pages  of  the  primary  geography — the  picture  of  the  south  sea  islander, 
clad  in  nothing  but  his  modesty  and  a  bunch  of  dried  grass  fastened  to 
his  loins  by  a  rawhide  throng.  Then  they  laughed  again,  But  the  rattle 
of  the  stamps  drowned  the  laugh,  and  the  stamps  kept  on  rattling.  As  a 
matter  of  fact,  the  New  Zealand  practice  did  not  prove  anything  for  Black 
Hills  ores,  for  there  they  treated  ore  that  previously  yielded  a  profit  with 
a  recovery  of  only  sixty-five  per  cent  by  dry  crushing  and  hot  pan  amalga- 
mation. (Trans.  Am.  Inst.  M.  E.  September,  1899.)  As  soon  as  the  old 
ramshackle  mill  up  the  gulch  showed  that  the  ore  could  be  treated  at  a 
profit  some  of  those  interested  wanted  to  put  up  a  big  mill,  just  like  the 
other  big  mills,  a  dry  mill,  of  course,  and  be  up  to  date  and  in  fashion. 
Now  it  is  a  safe  and  most  laudable  thing  in  mill  construction  to  keep  as 
near  as  possible  to  the  beaten  path.  This  cannot  be  too  strongly  impressed 
upon  the  mind  of  every  man  who  has  in  his  hands  the  disposal  of  a  com- 
pany's capital.  It  is  better  and  safer  to  allow  the  "other  fellow"  to  do  as 
much  of  the  experimenting  as  possible.  But  when  a  mill  man  becomes 
afflicted  with  an  idea,  and  covered  with  mud,  fashion  counts  for  very  little 
indeed.  So  the  stamps  kept  on  rattling  until  they  won  out  and  the  result 
was  the  mill  of  the  Dakota  Mining  and  Milling  Company  now  running  in 


100  Black  Hills  Mining  Men's  Association. 

Deadwood  and  probably  capable  of  treating  ore  at  a  less  cost  than  any 
other  fine  crushing  mill  in  the  world,  excepting  of  course,  the  plants  treating 
free  milling  ore.  Before  these  first  experiments  had  proceeded  very  far, 
however,  the  Portland  Company  leased  a  stamp  mill  at  Gayville,  and  put 
the  process  in  operation  with  important  improvements. 

One  important  characteristic  of  this  process  is  the  separate  treatment 
of  the  sands  and  slimes,  which  on  the  score  of  economy  presents  an  appar- 
ent contradiction.  The  carrying  out  of  two  materially  different  processes 
in  the  same  mill  calls  for  a  greater  first  cost  of  the  plant  as  well  as  more 
detail  in  its  operation,  but  I  am  ready  to  predict  that  separate  treatment 
is  destined  to  be  the  rule  of  practice  with  the  siliceous  ores  of  the  Black 
Hills.  There  will  probably  be  exceptions  to  this  rule  in  the  form  of  well 
conducted  mills  favored  with  a  uniform  supply  'of  ore  of  special  quality, 
but  exceptions  often  prove  a  rule.  The  discussion  of  the  general  question 
of  separate  treatment  opens  a  large  and  interesting  field  of  study.  A  mill 
should  be  as  free  from  complexity  of  details  as  is  consistent  with  autom- 
atism. However  automatic  operation  does  not  always  mean  the  highest 
economy.  It  is  easy  to  overestimate  the  value  of  a  machine  process.  There 
are  many  persons  besides  Helen's  babies  that  like  to  see  the  wheels  go 
round,  and  this  common  weakness  of  human  nature  is  responsible  for  an 
enormous  amount  of  misdirected  effort  in  the  building  of  thousands  of 
complicated  machines  that  cost  many  times  more  than  they  are  worth. 
In  following  this  idea  of  doing  things  by  machinery,  the  earlier  attempts 
at  eyaniding  were  along  the  lines  of  barrel  chlorination  somewhat  hastening 
the  process,  to  be  sure,  but  it  W7as  soon  found  that  in  addition  to  the  high 
cost  and  limited  capacity  of  the  barrel  it  cost  good  money  to  turn  that 
barrel.  Various  agitating  devices  have  been  tried,  but  while  the  political 
agitator,  the  spiritual  agitator,  the  social  agitator,  and  many  other  choice 
brands  of  agitators  seem  to  have  their  field  of  usefulness,  the  man  who 
seeks  to  agitate  wet  sand,  by  mechanical  means  at  least,  has  not  so  far 
succeeded  in  dazzling  the  world  by  his  exploits.  The  best  profit  margin 
is  usually  made  by  the  man  who  allows  his  sand  to  run  into  a  big  leaching 
vat,  and  then  leaves  it  alone.  A  chemically  active  solution  is 'actively 
percolating  through  the  sand  by  gravity  which  costs  nothing.  After  deposit- 
ing its  values  in  the  zinc  box,  this  solution  oxygenated,  aerated  and  other- 
wise rejuvenated,  spits  on  its  hands,  and  again,  and  then  again,  goes  after 
that  sand  until  we  obtain,  as  everybody  knows,  the  customary  extraction 
of  104  per  cent,  more  or  less.  During  all  this  time  the  mill  man  has  been 
leaving  the  sand  alone,  and  giving  his  solution  a  chance.  Oh,  how  many 
knotty  problems  would  find  a  ready  solution  if  we  could  only  give  the 
solution  a  chance.  How  many  of  us  would  be  benefited  in  mind,  body 
or  estate  if  we  had  only  known  when  to  leave  even  a  good  thing  alone. 
It  is  a  little  humiliating  to  note  that  with  all  our  twentieth  century  advance- 
ment we  have  been  forced  to  go  so  far  back  to  first  principles  in  the  treat- 
ment of  wet  sand — that  we  have  not  materially  advanced  beyond  the  ash 
barrel  stage  of  leaching  as  probably  first  practiced  by  Mother  Eve  when 
she  made  her  first  batch  of  soft  soap,  and  soft-soaped  Adam  into  eating 


Black  Hills  Mining  Men's  Asgovialibn?  '.'>',,        101 

that  apple  that  gave  him  such  a  thirst  for  more  knowledge  and  such  a  desire 
to  "see  the  wheels  go  round."  But  this  is  where  we  are  at,  for  the  present 
at  least,  and  as  far  as  sand  is  concerned,  is  the  conclusion  of  the  whole 
matter. 

To  many  this  declaration  may  seem  rather  sweeping,  particularly  in 
these  days  of  improvement  and  discovery,  but  I  feel  that  it  is  a  safe  state- 
ment of  a  general  rule.  A  general  truth  or  a  general  rule  has  exceptions. 
For  instance,  with  separation  of  slimes  and  cleaner  sand  the  tendency  is 
toward  higher  leaching  vats  and  deeper  ore  charges.  Now  a  good  mill 
man  will  see  that  his  solution  carries  plenty  of  free  oxygen  before  it  is  put 
into  the  sand,  but  with  certain  iron  compounds  in  the  ore,  or  for  other 
reasons,  there  may  not  be  enough  oxygen  to  last  down  through  a  deep 
charge,  or  any  charge  with  a  slow  leaching  rate.  The  result  may  appear 
in  low  extraction,  particularly  near  the  bottom  of  the  vat.  A  convenient 
remedy  might  be  found  in  the  introduction  of  compressed  air  at  some  stage 
of  the  process,  which  is  probably  as  well  effected  under  and  through  the 
filter  cloth  as  by  a  special  system  of  perforated  pipes.  The  consequent 
slight  movement  and  rearrangement  of  the  ore  particles  would  be  a  benefit 
in  some  cases,  in  fact  a  cheap  substitute  for  the  South  African  system  of 
double  treatment  where  the  sand  is  shoveled  into  a  second  vat  to  undergo 
a  second  leaching.  However,  with  a  clean  material  thoroughly  freed  from 
slimes  the  apparent  advantage  of  moving  the  sand  might  disappear. 

But  all  crushed  ore  is  not  sand.  "Ay!  there's  the  rub."  Many  kinds 
of  rock  are  prone  to  break  into  an  almost  impalpable  powder  called  dust 
by  the  ordinary  mortal,  but  universally  known  as  "slimes"  among  the 
demons  who  infest  wet  crushing  mills.  Some  years  ago  ores  that  slimed 
badly  were  not  generally  regarded  as  amenable  to  treatment  by  wet  ex- 
traction methods.  Then  came  improvements  in  crushing  rolls  until  they 
became  perfect  marvels  of  the  mechanics  skill,  expensive  to  buy  and  more 
expensive  to  maintain,  but  by  the  gradual  reduction  method,  with  a  careful 
arranged  system  of  screening  between  each  break  they  did  the  work  where 
other  means  failed,  produced  a  fairly  leachable  pulp  and  scored  a  sub- 
stantial advance  in  metallurgical  progress.  But  some  ores,  particularly 
the  siliceous  ores  of  the  Black  Hills,  were  found  to  require  very  fine  crush- 
ing, and  then  the  old  trouble  reappeared — too  much  dust,  imperfect  leach- 
ing, and  uncertain  recovery  of  values.  Men  some  time  ago  learned  not  to 
agitate  sand  on  account  of  the  expense,  and  later  after  many  failures  with 
a  thousand  patented  devices  have  generally  learned  not  to  attempt  the 
leaching  of  slimes.  The  only  exception  that  may  be  taken  to  this  statement 
seems  to  be  in  favor  of  the  filter  press,  which,  however,  has  so  far  only 
found  favor  in  the  treatment  of  tolerably  high  grade  material.  However, 
it  is  possible  that  important  improvements  may  yet  be  made  in  this  rather 
forbidding  direction. 

In  mills  where  there  were  no  special  facilities  for  slimes  treatment  the 
practice  has  been  in  some  cases  to  allow  as  much  dust  as  possible  to  go 
out  of  the  windows,  or  into  the  lungs  of  the  workmen.  In  some  cases 
this  dust  carried  exceptionally  high  values,  but  in  going  to  waste  it  prob- 


102  Black  Hills  Mining  Men's  Association. 


ably  gave  the  company  a  better  net  profit  than  if  allowed  to  go  into  the 
already  slimy  vat  charge. 

It  is  hardly  necessary  to  mention  the  fact  that  a  much  greater  amount 
of  dust  may  be  allowed  in  roasted  material  without  harm.  At  a  lowr  red 
heat  the  water  of  hydration  is  driven  from  the  aluminous  and  clayey  con- 
stituents of  ore.  During  the  after  treatment  with  aqueous  solutions  the 
water  will  not  again  combine  to  make  a  plastic  or  tenacious  material,  the 
dehydrated  silicates  having  the  physical  character  of  sand,  even  when 
crushed  as  fine  as  200  mesh. 

However,  we  can  not  afford  to  roast  simply  to  secure  better  leaching, 
and  this  brings  us  face  to  face  with  the  problem  of  treating  the  slimes 
separately.  As  to  the  precise  method,  it  is  probable  that  we  are  on  the 
right  track  in  "leaving  them  alone,"  as  much  as  possible,  just  run  them 
into  a  big  tank,  allowr  the  solids  to  settle  and  the  gold  solution  to  decant, 
then  various  washes,  ad  infinitum,  ad  nauseam.  That  is  the  most  prev- 
alent system,  the  one  used  here  and  today  regarded  the  world  over  as 
good  practice. 

But  the  treatment  of  slimes  presents  an  inviting  field  for  further  re- 
search, and  in  this  the  Black  Hills  men  have  not  been  idle.  Mr.  D.  C. 
Boley  has  been  working  with  his  characteristic  energy  on  the  subject  fcr 
the  past  year.  He  has  completed  and  taken  out  a  patent  for  a  machine 
operated  on  the  principle  of  forced  percolation  by  air  pressure  while  the 
material  is  thinly  spread  on  a  filter.  It  has  many  strong  points  from  a 
theoretical  view,  but  Mr.  Boley,  realizing  that  such  things  sometimes  develop 
weak  points  in  practice,  has  leased  a  small  mill  for  the  purpose  of  trying 
the  invention  on  a  working  scale.  Whether  or  not  his  machine  is  found 
to  be  an  improvement  over  all  other  methods,  his  careful  and  painstaking 
efforts  will  materially  add  to  the  stock  of  human  knowledge  on  an  interest- 
ing subject. 

The  Portland  mill  has  developed  an  arrangement  in  the  bottom  of  its 
slimes  tanks  which  introduces  the  wash  somewhat  on  the  principle  of  a 
revolving  lawn  sprinkler  and  is  said  to  effect  an  extremely  thorough  agi- 
tation of  the  charge.  It  may  assume  the  place  in  popular  favor  so  long 
held  by  the  more  common  centrifugal  pump,  and  if  so,  will  obviate  the 
pumping  of  the  charge  to  a  different  tank  at  each  wash,  which  by  most  mill 
men  is  regarded  necessary  in  order  to  make  sure  of  thorough  mixing. 

It  has  always  seemed  to  the  writer  of  this  article  that  the  decantation 
process  being  the  most  natural  and  in  itself  requiring  no  machinery  what- 
ever— just  let  the  mud  stand  and  settle — is  most  likely  to  prove  economical 
in  practice.  But  as  now  carried  on  intermittently  by  separate  tank  charges, 
there  is  valuable  time  lost  in  charging,  agitating  and  discharging,  besides 
the  labor  involved,  and  the  needless  storage  and  rehandling  of  the  bulky 
washes  required.  Now  if  we  could  make  this  process  continuous,  so  that 
the  entire  area  of  the  settling  tanks  will  be  continuously  employed  in 
settling  the  suspended  material,  it  would  leave  little  to  be  desired  and 
certainly  nothing  more  to  be  attained  in  decantation.  It  would  materially 
cut  down  the  floor  space  required,  save  labor  and  require  practically  no 


Black  Hills  Mining  Men's  Association.  103 

storage  capacity  for  washes.  In  pursuance  of  this  train  of  reasoning  an 
ordinary  pointed  box  .settler  was  last  fall  put  in  at  the  mill  of  the  Highland 
Chief  Mining  Company,  then  just  put  in  operation  by  the  writer  as  a  wet 
crushing  cyanide.  The  box  was  designed  for  the  continuous  separation 
of  the  slimes  from  the  battery  solution-  It  was  a  small  affair,  having  only 
about  100  square  feet  of  settling  surface  yet  it  handled  about  eight  tons 
of  dry  solids  per  day,  while  the  regular  settling  tanks  of  the  same  surface 
area  and  having  a  capacity  of  thirty  metric  tons  liquid,  required  to  stand 
undisturbed  twenty-four  to  thirty  hours  to  settle  five  to  six  tons  of  solids. 
An  interesting  feature  of  the  pointed  box  was  its  capacity  to  decant  an 
enormous  quantity  of  liquid  without  retarding  the  subsidence  of  the  solids. 
In  fact  its  decanting  capacity  could  not  be  ascertained  as  it  was  not  practi- 
cable to  deliver  to  it  more  than  200  tons  of  battery  solution  per  day.  The 
regular  slimes  tanks,  having  three  times  the  cubic  capacity  could  not  turn 
off  more  than  twenty  tons  of  wash  in  the  same  length  of  time. 

This  of  course  suggested  that  a  large  quantity  of  wash  can  be  used 
in  a  continuous  apparatus,  while  by  the  intermittent  process  a  large  wash 
means  a  very  big  tank  for  a  small  quantity  of  slimes.  In  the  operation 
of  this  box  a  number  of  important  facts  were  observed  and  checked,  some 
of  them  opposed  to  conceptions  which  often  control  the  design  of  settling 
tanks  for. mill  work,  and  this  has  encouraged  the  writer  to  undertake  the 
design  of  a  continuous  apparatus  for  washing  and  extracting  the  values 
from  slimes.  It  has  been  made  the  basis  of  patent  applications,  numbered 
108,722,  and  111,049,  series  of  1900,  embracing  some  fifteen  claims  and  con- 
taining quite  a  number  of  long  words  required  by  the  rules  of  the  Patent 
Office  in  such  case  made  and  provided.  A  small  fraction  of  one  percent, 
of  all  the  patents  issued  in  this  country  find  their  way  into  practice,  and 
it  is  therefore  possible,  barely  possible,  that  this  apparatus  may  again  be 
heard  from. 

This  interesting  subject  can  not  be  discussed  farther  within  the  usual 
limits  of  a  paper  of  this  kind,  and  I  must  therefore  close,  thanking  you, 
gentlemen,  for  your  kind  attention. 

The  paper  was  very  well  received,  and  Mr.  Randall  congratulated  by 
all  who  heard  him  on  the  excellence  of  his  paper,  and  voted  the  thanks  of 
the  association. 

The  meeting  then  adjourned  to  the  ante-room,  where  a  nice  lunch 
awaited  the  discussion  of  the  members  and  their  visitors. 


104  Black  Hills  Mining  Men's  Association. 

PYRITE  ORES  AND  THEIR  SMELTING. 

BY  DR.  FRANKLIN  R.  CARPENTER. 

[Paper  prepared  for  American  Mining  Congress,  Deadwood  and  Lead,  South 
Dakota,  September  7  to  12,  1903.] 

This  is  a  process  of  smelting  applicable  to  any  raw  ores  not  carrying 
lead,  but  more  especially  to  sulphide  ores  carrying  copper. 

From  time  immemorable  man  has  roasted  off  the  sulphur  in  pyrite  ores 
and  burned  his  iron  to  oxide  in  the  open  air,  thus  wasting  what  pyritic 
smelters  consider  good  fuel.  If  it  is  admitted  that  a  heat  unit  derived 
from  the  oxidation  of  iron  or  sulphur  will  do  as  much  work  as  one  derived 
from  the  oxidation  of  coke,  the  folly  of  this  proceeding  becomes  apparent, 
provided  this  heat  can  be  utilized.  If  it  can,  one  might  just  as  well  waste 
his  coke  in  a  similar  manner. 

American  engineers  derived  from  Europe  two  raw  smelting  processes, 
which,  unfortunately,  are  often  confused.  One  was  the  Kongsberg  process 
of  pyritic  smelting,  where  raw  pyrite  was  added  to  the  charge  simply  to 
produce  a  carrier,  or  matte,  for  the  precious  metals.  This  was  all  I  had 
in  vifiw  when  I  advocated  pyritic  smelting  for  the  siliceous  ores  of  South 
Dakota.  By  its  means  the  small  amounts  of  gold  and  silver  in  many  tons 
of  rock  were  concentrated  into  a  few  tons  of  matte.  This  process,  broadly, 
is  very  ancient;  so  ancient  that  we  know  not  when  it  was  first  employed. 
It  will  be  observed  later  that  it  is  the  very  opposite  of  the  other  class  of 
pyritic  smelting,  in  that  the  ores  treated  are  siliceous,  and  pyrite  is  added 
for  a  carrier  only. 

The  other  sort  of  pyritic  smelting  is  the  out-growth  of  principles  dis- 
covered by  Sir  Henry  Bessemer  in  steel  making,  who  found  that  cast  iron 
might  be  purified  by  the  oxidation,  or  burning  of  its  own  contained  im- 
purities. The  principles  of  Bessemer,  much  modified,  are  now  everywhere 
applied  to  the  refining  of  copper  matte,  where  again  the  oxidation  of  the 
iron  and  sulphur  furnish  the  heat  to  burn  the  slag  off  impurities,  giving 
us  a  very  pure  blister  copper  at  one  direct  cheap  operation,  and  without 
additional  fuel.  This  is  the  beautiful  operation  of  Mahnes,  first  employed 
in  America  by  our  Butte  friends. 

After  the  establishment  of  Bessemer's  process  in  England,  Hollway 
sought  to  smelt  the  Rio  Tinto  copper  sulphide  ores  by  means  of  the  heat 
generated  in  the  oxidation  of  their  sulphur  and  iron.  A  short  calcula- 
tion will  show  that  his  conclusions  were  well  founded.  Without  going 
into  the  investigation  very  fully,  we  may  admit  that  one  pound  of  iron 
pyrite  burned  in  the  furnace  is  equal  to  2,026  B.T.  U.,  and  that  this,  roughly, 
is  equal  to  forty  per  cent  of  the  value  of  a  pound  of  carbon  burned  to  CO; 
but  as  our  furnaces  probably  burn  perhaps  a  third  of  the  carbon  to  CO2, 
we  may  conclude  that  this  value  is  too  high,  hence  figure  it  as  equal  to  only 
twenty-six  per  cent,  or  one-fourth  the  value  of  one  pound  of  coke,  which 
is  certainly  a  safe  deduction. 


Black  Hills  Mining  Meris  Association.  105 

Those  who  are  interested  in  the  subject  are  referred  to  the  forthcoming 
volume  of  the  Mineral  Industry,  where  Mr.  E.  C.  Reybold,  Jr.,  a  young 
man  employed  at  our  Golden  Works,  and  formerly  with  me  at  Deadwood 
has  fully  investigated  the  subject. 

For  every  four  pounds  of  pyrite,  therefore,  burned  in  the  open  air,  we 
have  lost  the  equivalent  of  one  pound  of  good  coke.  Stated  in  another  way, 
four  pounds  of  pyrite  will  do  as  much  smelting  as  one  pound  of  coke,  and 
in  so  doing,  it  is  smelted  and  fluxed  itself. 

Our  blast  furnaces,  in  ordinary  matte  smelting,  are  running  with  six- 
teen per  cent  coke,  but  a  charge  containing  sixty-four  per  cent  of  raw  pyrite 
should  smelt  itself;  and  if  this  is  assisted  with  a  hot  air  stove,  which  can 
be  fired  with  a  cheap  low-grade  fuel,  even  this  percentage  of  pyrite  may  be 
much  reduced.  The  fullest  application  of  these  principles  has  been  made 
by  Mr.  Robert  Steicht  at  Mount  Lyell  in  Tasmania,  where  the  first  smelting 
is  done  absolutely  without  carbonaceous  fuel  of  any  sort.  Let  us  now 
consider  for  a  moment  what  they  do.  Their  ores  are  pyritic,  and  of  two 
classes.  The  Mount  Lyell  pyrite  is  so  mined  as  to  maintain  a  general 
average  as  follows: 

Fe,  40.30  per  cent. 
SiO2,  4.42  per  cent. 
BaSO4,  1.48  per  cent. 
Cu,  2.36  per  cent. 
Al2Os,  2.04  per  cent. 
S,  46.01  per  cent. 
Ag.  2  ounces  per  ton. 
Au,  0.0725  ounces  per  ton. 

The  second  class  is  a  siliceous  bornite  ore  purchased  from  other  mines, 
and  quartz  is  employed  as  a  flux.  This  is  the  direct  opposite  of  the  case 
first  considered,  calling  for  additions  of  silica  in  the  place  of  additions  of 
pyrite. 

The  Mount  Lyell  Company  operates  eleven  blast  furnaces  which  are 
arranged  in  two  smelting  plants.  Those  employed  in  the  first  smelting  are 
five  in  number,  and  are  42x210  inches  at  the  tuyeres.  The  height  of  the 
ore  column  above  the  tuyeres  is  maintained  at  nine  feet  and  six  inches. 
The  other  plant  consists  of  six  furnaces,  five  of  which  are  40x168  inches 
at  the  tuyeres.  The  tuyeres  are  all  three  inches  in  diameter,  and  the 
larger  furnaces  have  thirty-two  each,  the  smaller  ones  twenty-four  each. 
In  the  first  set,  of  furnaces  all  the  ore  delivered  at  the  plant  is  smelted 
without  roasting  and  without  fuel,  to  a  first  matte  carrying  fifteen  per  cent 
copper.  Formerly  a  hot  blast,  528  degrees,  and  three  per  cent  coke  were 
used.  But  for  a  year  past  the  coke  has  been  abandoned  and  the  blast 
only  warmed.  No  difference  was  noticed  in  this  change  save  a  greatly 
increased  capacity — three  furnaces  now  doing  the  work  of  four  under  the 
old  method. 

The  matte  from  this  first  smelting  is  re-smelted  in  the  second  set  of 
furnaces  to  a  forty-five  to  fifty  per  cent  copper  matte,  which  goes  directly 
to  the  converters. 


106  Black  Hills  Mining  Men's  Association. 

The  process  is,  therefore,  divided  into  three  stages,  all  of  which  are 
oxidizing,  and  which  may  be  said  to  be  almost  continuous  Bessemerizing 
from  beginning  to  end.  Disregarding  the  time  for  cooling  and  transporta- 
tion from  one  department  to  another,  the  time  consumed  from  ore  to  copper 
is  only  six  hours,  and  this  is  accomplished  almost  without  extraneous  fuel. 

In  the  first  smelting  no  limestone  or  coke  is  used,  and  but  a  slightly 
warmed  blast.  In  the  second  smelting  a  small  percentage  of  coke  and 
limestone  is  used,  and  a  cold  blast.  The  third  stage  is  simple  Bessemeriz- 
ing or  converter  work. 

These  results  having  been  attained  at  Mount  Lyell  by  the  application 
of  principles  long  advocated  by  pyritic  smelters,  there  is  no  longer  any 
reason,  in  my  opinion,  why  the  same  or  similar  results  cannot  be  had  at 
Sudbury,  Ontario,  Ducktown,  Tenn.,  Keswick,  California,  and  in  Arizona 
and  New  Mexico — in  fact,  at  any  place  where  the  ores  carry  sufficient  pyrite, 
or  pyrite  can  be  had  from  outside  sources. 

It  will  be  observed  that  the  smelting  proper  at  Mount  Lyell  is  accom- 
plished in  two  steps.  A  low-grade  matte  is  made  in  the  first  smelting,  which 
is  enriched  by  a  second  smelting  to  a  grade  high  enough  for  the  converter. 
This,  in  a  differently  constructed  charge,  may  not  be  necessary,  depending 
upon  the  per  cent,  of  copper,  degree  of  concentration  and  the  proportion 
of  iron  to  silica.  A  charge  can  be  made  of  Montana  ores  which  will  not 
require  the  second,  or  concentration  smelting;  but  the  second  smelting, 
being  relatively  small  compared  with  the  first,  is  never  a  serious  matter 
and  adds  but  little  to  the  cost. 

I  have  now  sketched  the  two  outside  cases  of  pyritic  smelting,  both 
of  which  are  eminently  successful  in  their  respective  fields.  There  are 
many  cases,  however,  which  lie  between  these  extremes,  as  at  Butte,  Mon- 
tana, in  Gilpin  County,  Colorado,  British  Columbia  and  elsewhere,  where 
the  sulphide  ores  carry  a  large  percentage  of  silica  and  are  treated  by  water 
concentration  before  smelting.  This  pre-supposes  concentration  mills  of 
enormous  capacity  and  roasting  furnaces  for  the  concentrates  so  obtained, 
both  of  which  cost  great  sums  of  money,  and  which  are  at  best  very  waste- 
ful. By  the  further  application  of  the  principles  already  developed  and 
the  utilization  of  the  cheap  fuel  now  wasted,  it  is  barely  possible  that  the 
process  might  be  modified. 

Modern  copper  smelting  methods  have  received  their  greatest  develop- 
ment at  Butte,  and  I  will  let  no  one  go  beyond  me  in  admiration  of  the 
great  work  done  there  and  sincere  respect  for  those  who  have  accomplished 
it.  Their  mills  are  models  of  mechanical  ingenuity  never  surpassed,  and 
their  reverberatory  furnace  work  is  not  equalled.  I  do  not  lose  sight  of 
the  fact  that  these  last  furnaces,  which  a  few  years  ago,  when  first  intro- 
duced from  Swansea,  had  a  hearth  capacity  of  but  9x14  feet,  and  a  smelt- 
ing capacity  often  as  low  as  ten  tons  per  day,  requiring  to  be  clayed  up 
every  twenty-four  hours,  have  now  been  developed  into  furnaces  having 
hearths  20x50  feet,  and  smelting  more  than  100  tons  each  in  twenty-four 
hours,  and  which  require  claying  not  more  than  once  in  twelve  days;  also 
that  they  save  more  than  fifty  per  cent  of  the  fuel  used  in  the  old  furnaces. 


Black  Hills  Mining  Men's  Association.  107 

It  is,  therefore,  with  the  greatest  diffidence  that  I  suggest  that  any  change 
is  possible  in  the  methods  of  a  camp  which  is  today  without  a  peer  in  the 
world  for  the  excellency  of  its  work,  but  let  us  not  forget  history. 

"The  old  order  changeth,  giving  place  to  new." 

Seemingly  small  things  in  metallurgy  have  often  accomplished  the 
greatest  results. 

A  few  years  ago  there  was  still  running  in  Savoy,  a  small  iron  blast 
furnace  blown  by  a  trompe,  or  box  in  which  falling  water  compressed  air 
by  entangling  it  in  its  fall — a  blower  which  we  may  readily  imagine  neither 
heated  the  air  nor  dried  it,  yet  the  addition  of  this  blowing  machine,  crude 
as  it  was,  made  the  instrument  which  put  out  of  blast  all  the  Catalan 
direct  furnaces  in  every  part  of  the  world.  Without  the  trompe  the  blast 
furnace  for  iron  would  probably  not  have  existed,  and  without  pig  iron 
all  that  is  known  to  us  now  as  the  "age  of  steel"  could  not  have  existed. 

Already  three-fourths  of  the  beautiful  ancient  Welsh  copper  process, 
with  its  roastings  and  re-smeltings,  to  which  the  reverberatory  furnace 
belonged,  has  gone  by  never  to  return — the  one  operation  of  converting 
having  replaced  them  all. 

I  believe  that  when  Hollway  undertook  to  smelt  the  Rio  Tinto  copper 
ores  without  fuel  other  than  what  they  themselves  contained,  he  laid  down 
a  principle  which  will  ultimately  make  every  copper  roasting  heap  and 
roasting  furnace  as  useless  as  the  Catalan  forge,  and  the  time  is  near  at 
hand  when  one  would  no  sooner  waste  his  good  iron  sulphide  fuel  than 
he  would  his  good  coke.  Already  more  ore  is  smelted  raw  at  Butte  than 
formerly.  The  first-class  copper  ore  and  the  coarse  concentrates  go -into 
the  blast  furnace  raw — a  tribute,  as  far  as  it  goes,  to  pyritic  smelting.  But 
if  the  prinicples  here  mentioned  are  correct,  the  large  concentrating  mills 
and  roasting  furnaces  will  gradually  be  replaced  by  a  process  that  is  all 
one  of  fire,  and  that  fire  largely  derived  from  the  oxidation  of  the  now 
wasted  pyrites. 

I  have  done  what  I  could  to  secure  the  actual  composition  and  cost  of 
treating  an  average  ton  of  Butte  ore  as  it  is  broken  at  the  mines,  that  I 
might  make  a  comparison  between  the  all-fire  raw  method  here  advocated, 
and  the  combination  water  concentration  smelting  method  now  employed. 

The  following  may  not  be  absolutely  correct,  but  it  will  do  for  com- 
parison. The  ores  of  this  district,  according  to  a  recent  paper,  are  mined 
in  two  classes.  fThe  first  are  said  to  average  from  ten  to  fifteen  per  cent 
copper,  and  to  constitute  ten  per  cent  of  the  ores  raised.  The  second  class 
comprises  the  remaining  ninety  per  cent,  and  yields  from  three  to  six  per 
cent  copper.  If  all  were  broken  down  together,  we  may  take  five  per  cent 
as  the  average,  and  thirty  to  forty  per  cent  silica  with  the  alumni,  alkalies, 
sulphur  and  iron  to  balance. 

I  have  arrived  at  the  present  cost  per  ton  of  ore  from  the  testimony 
of  Mr.  Frank  Klepetko,  in  March,  1898. 

Dressing  (or  water  concentration),  per  ton  of  ore,  $0.82.  Roasting  con- 
centrates derived  from  a  ton  of  ore,  $0.38.  Smelting  calcines,  $1.20.  Total 
per  ton  of  original  ore,  $2.40. 


108  Black  Hills  Mining  Men's  Association. 

In  the  water  concentration  he  stated  the  loss  to  be  eighteen  per  cent. 
In  the  roasting,  2.6  per  cent.  In  the  smelting,  4.2  per  cent.  Total,  24.8 
per  cent. 

With  copper  at  fourteen  cents  per  pound,  this  is  worth  $3.47,  making 
the  total  cost,  including  losses,  $5.87  per  ton  of  original  ore. 

If  this  ore  were  smelted  direct  as  it  comes  from  the  mine,  without  con- 
centrating or  roasting,  by  the  addition  of  limestone  and  coke  and  the  ap- 
plication of  hot  blast,  it  would  cost  fully  as  much  per  ton  of  ore,  perhaps 
more;  but  I  am  sure  that  $3.00  per  ton  will  cover  it.  This  is  more  per  ton, 
but  I  estimate  a  greater  saving.  According  to  the  above  statement  there 
was  lost,  in  the  concentrating,  roasting  and  smelting  24.8  per  cent  of  the 
original  contents  of  the  ore  by  the  time  the  copper  was  raised  to  a  grade 
sufficiently  high  for  the  converters — against  which  I  figure  but  nine  per 
cent  in  direct  smelting,  leaving  a  difference  of  $3.47  minus  $1.26,  equal  to 
$2.21  gain  per  ton.  As  this  gain  is  wholly  in  the  copper,  it  adds  a  propor- 
tional length  of  life  to  the  mines.  If,  however,  the  one  smelting  cannot  be 
done  for  the  cost  of  concentrating,  roasting  and  smelting,  this  gain  would 
be  reduced  by  the  difference.  If  the  first  smelting  cost  $3.00,  which  I  am 
sure  is  ample,  we  should  still  have  a  gain  of  $1.60  in  favor  of  raw  smelting, 
always  supposing  these  figures  to  be  correct. 

In  our  prejudice  for  the  established  methods,  it  will  be  well  to  remember 
a  story  told  by  a  traveler  from  the  Sahara  Desert.  He  came  across  a  party 
of  Arabs  making  iron — doubtless  after  a  manner  dating  from  the  days  of 
Abraham.  TJie  furnace  consisted  of  a  hole  in  the  ground,  around  which 
were  three  blowing  engines,  each  consisting  of  an  Arab  with  a  long  tube, 
one  end  of  which  was  in  his  mouth  and  the  other  in  the  furnace.  After 
blowing,  from  six  to  eight  pounds  of  iron  per  shift  was  obtained. 

Our  traveler  was  much  impressed,  but  inquired  of  the  boss  metallurgist, 
"Why  do  you  use  this  method  of  making  iron?"  He  received  a  look  of 
withering  scorn  and  the  reply,  "What  other  method  can  there  be?  Neither 
our  fathers  nor  ourselves  ever  heard  of  any  other." 

Because  our  fathers  and  ourselves  have  always  burned  our  iron  and 
sulphur  outside  of  the  furnace  is  no  good  reason  for  continuing  it. 


110  Black  Hills  .lining  Meris  Association. 

MATTE  SMELTING. 

BY  PAUL  DANCKWARDT,  SUPERINTENDENT  GOLDEN  REWARD  SMELTER. 
[Read  before  Black  Hills  Mining  Men's  Association,  July  24th,  1902.] 
GENTLEMEN: 

The  process  of  matte  smelting,  which  I  have  chosen  for  the  subject 
of  this  evening's  paper,  is  rather  an  old  affair  for  the  Black  Hills  people ; 
it  is  practically  one  of  the  first  processes  introduced  here  to  solve  the  problem 
of  extracting  the  values  from  our  ores.  But  however  old  the  process  of 
matte  smelting,  often  perversely  called  the  "pyritic  process,"  may  be,  it 
has  doubtless  achieved  vast  results,  and  on  account  of  this  and  the  fact 
that  this  process  generally  everywhere  else  is  in  a  state  of  rapid  improve- 
ment and  expansion,  it  may  be  worth  while,  to  state  here  what  we  have 
done  in  all  these  years,  what  we  are  doing  and  what  can  be  done  for  the 
future  of  this  process  as  far  as  the  Black  Hills  conditions  are  concerned. 

As  this  process  of  ore  reduction  is  only  by  one  company  successfully 
applied  in  the  Black  Hills,  there  is  no  competition  in  this  field  of  metallurgy 
right  here.  And  consequently  no  basis  for  exhaustive  discussions  of  the 
pro  and  con,  as  we  used  to  hear  them  with  regard  to  the  cyanide  process. 
The  cyanide  process  forms  indeed  at  present  the  topic  of  the  day,  but  both 
processes  have  their  special  field  of  application.  Taking  all  the  different 
classes  of  ore  into  consideration,  we  may  shortly  say,  that  both  processes 
together  will  obtain  the  best  result. 

When  matte  smelting  was  first  introduced  in  these  Hills,  there  seemed 
to  exist  a  confusion  of  ideas  as  to  tlie  name,  under  which  the  "new"  process 
was  to  be  launched.  Even  patents  were  taken  out,  but  at  last  the  truth 
dawned,  and  at  present  we  hear  nobody  claim  to  have  invented  this  good 
old  process,  called  matte  smelting,  because  it  is  too  old  to  have  parents 
living  in  our  generation.  But  this  statement  shall  not  say  that  we  are 
doing  today  exactly  the  same  thing  that  has  been  done  a  hundred  years 
ago  or  that  no  exertion  has  been  made  to  change  or  improve  the  old  way 
of  working  this  process.  On  the  contrary,  there  have  been  expended 
thousands  of  dollars  and  lots  of  brain  power  to  make  out  of  the  good  old 
process  with  limited  applicability  one. that  is  now  fit  for  competition  on  a 
widely  enlarged  field.  These  changes  are  not  fully  recorded  in  our  text 
books  and  the  lay  man  or  merely  book-learned  individual  hardly  conceives 
the  extent  of  the  improvements  made  since  its  introduction  into  this  country. 
Today  even,  we  cannot  state  yet  that  the  time  of  transition  for  this  process 
has  past  already. 

If  we  begin  now  with  the  first  question:  What  have  we  done  since  the 
old  D.  &  D.  smelter  started?  I  may  say,  that  we  have  tried  everything. 
One  experiment  followed  another,  and  credit  to  the  capitalists  and  the 
managers  for  their  persistency  in  their  work  and  money  consumed-  Soon 
we  would  make  an  iron  matte,  soon  a  lead  matte,  soon  we  smelted  lead, 
soon  iron,  commonly  called  "sow,"  and  someone  considered  that  the  only 
possibility  of  solving  the  problem.  Slags  were  changed  and  the  furnaces 


Black  Hills  Mining  Men's  Association.  Ill 

tested  for  what  they  could  and  could  not  do,  until  they  were  frozen  solid 
from  top  to  bottom.  Muscular  smelting  played  an  important  factor  during 
the  infancy  of  the  works.  At  last  we  settled  down  on  a  slag  containing 
about  forty  per  cent  silica,  thirteen  per  cent,  ferrous  oxide,  and  the  re- 
mainder alumina,  lime  and  magnesia,  the  lime  prevailing.  We  could  now 
at  least  adjust  our  coke  to  a  certain  amount  of  material  to  be  smelted,  and 
often  we  stuck  too  tenaciously  to  the  sogained  rule,  sometimes  to  the 
disadvantage  of  the  company  financially.  For  there  were  other  points  to 
be  settled,  which  had  just  as  much  bearing  on  the  running  of  the  furnaces 
as  amount  or  quality  of  the  coke  and  slag  forming  material  alone.  When 
during  the  first  years  of  the  operation  of  the  works  an  iron  matte  was  made, 
the  furnaces  sometimes  ceased  providing  this  desirable  compound  suddenly, 
and  consequently  the  slags  would  run  up  in  gold  and  silver  values,  there 
being  no  carrier  for  them.  The  men,  even  the  head  men,  used  to  say, 
"the  matte  is  hanging  up  somewheres,"  because  they  noticed  sometimes 
afterwards,  that  the  furnaces  suddenly  changed  and  would  start  to  make 
such  an  amount  of  matte,  that  neither  furnace  nor  forehearth  bottom 
would  stand  the  corroding  action  of  the  gushing  iron  compound.  If  this 
was  the  end  of  it,  there  remained  nothing  to  be  done  but  jump  and  the  let 
elements  cool  down  again.  But  more  often  it  happened  that  the  tragedy 
closed  in  the  form  of  a  gradual  freeze  up.  The  matte  actually  did  not  hang 
up  to  any  great  extent  at  the  beginning  of  the  freeze  up,  and  might  have 
been  forced  to  reappear,  as  the  iron  compounds  of  the  charge,  principally 
pyrites,  were  simply  burning  off,  there  being  no  proper  proportion  between 
air  blast  and  coke.  When  thus  the  formation  of  the  matte  ceased,  the 
gold  and  silver  of  course  could  not  do  anything  but  run  off  with  the  slag. 
This  was  a  great  drawback,  but  happily  this  condition  of  affairs  could  not 
exist  very  long,  because  the  furnace,  as  if  it  had  a  soul,  that  cannot  see 
the  values  spoiled  in  such  a  way,  would  either,  if  conditions  were  favor- 
able, correct  itself,  or  cease  to  work  altogether.  This  latter  was  to  be  the 
end  of  it,  if  the  matte  did  not  start  to  run  again,  as  there  was  then  nothing 
running  down  to  keep  the  furnace  bottom  hot  enough  for  regular  work. 

Both  these  often  occurring  freeze  ups  and  the  temporary  appearance 
of  a  high  slag,  had  to  be  avoided  in  the  future.  Therefore  experiments 
were  made  with  a  copper  matte.  The  good  effect  of  this  was  evident,  but 
I  for  my  part  would  have  looked  for  other  means  of  obtaining  the  same 
result,  as  the  use  of  copper  ore  is  at  times  a  great  expense,  which  is  not 
always  outweighed  by  the  gain  in  saving  of  valuable  metals.  Since  I  have 
had  charge  of  the  plant  I  have  therefore  cut  the  copper  down  to  a  few  per 
cent  and  obtain  the  much  desired  regularity  of  flow  of  matte  by  giving  at 
intervals,  in  accordance  with  the  general  condition  of  the  furnace,  a  charge 
high  in  iron  and  of  great  heating  power. 

Up  to  this  time,  when  the  change  from  iron  to  copper  matte  was  ar- 
ranged, the  furnaces  were  run  at  a  low  air  pressure,  the  output  of  the  mill 
being  consequently  small.  The  following  introduction  of  an  increase  of 
pressure  raised  the  capacity  considerable. 

The  same  effect  had  the  installation  of  larger  furnaces.  But  in  spite 
of  all  these  improvements  the  furnaces  often  happened  to  make  only  short 


112  Black  Hills  Mining  Men's  Association. 

runs.  Often  a  freeze  up  would  occur  right  after  the  blow  in,  and  the  men 
at  the  head  could  not  always  give  an  explanation  for  such  accidents.  It 
should  have  been  evident,  that  a  furnace  running  at  such  a  high  silica  and 
low  iron  slag,  has  to  be  treated  in  an  altogether  different  way  than  a 
copper  or  lead  furnace  when  blown  in.  At  this  time,  when  the  bottom 
is  cold,  the  jackets  not  yet  or  only  slightly  crusted  with  slag,  and  the  charge 
loose,  there  is  great  danger  from  losing  heat.  The  furnace  ought  to  be 
watched  very  closely,  as  otherwise  the  coke  will  burn  off,  before  the  charge 
is  melted,  and  the  partially  melted  charge  enwrapping  part  of  the  coke 
will  fill  the  bottom  up  rapidly.  This  is  the  time  when  the  furnace  man 
can  show  his  capability.  It  is  sometimes  hard  to  find  the  fault  before  it 
is  too  late,  the  only  indications  being  the  condition  of  the  tuyeres  and  the 
appearance  of  the  top  of  the  furnace  and  the  temperature  of  the  jackets. 
There  existed  formerly  the  idea,  that  it  was  dangerous  to  try  the  tuyeres 
right  after  blowing  in,  and  even  later  on,  when  the  bottom  was  up  to  its 
full  heat,  the  punching  was  not  resorted  to,  except  a  tuyere  would  fill  up 
with  molten  slag.  This  was  altogether  wrong.  At  present  the  tuyeres  of 
all  the  furnaces  are  tested  every  morning  in  the  presence  of  the  super- 
intendent, and,  if  deemed  necessary,  even  out  of  the  time.  Only  a  careful 
examination  will  make  a  correct  diagnosis  and  the  application  of  the  proper 
remedy  possible.  The  condition  of  the  top  will  show  best,  whether  there 
is  too  much  or  too  little  coke,  when  taken  into  consideration  together  with 
the  condition  of  the  tuyeres.  Any  bad  tuyeres  should  be  turned  off  right 
away;  if  the  number  is  too  great,  only  part  of  them,  preferably  those 
adjoining  some  tuyeres  having  good  fire,  in  order  to  give  the  fire  a  chance 
to  get  down  again  to  the  tuyere  level.  The  jackets  should  in  the  beginning 
always  be  rather  warm. 

These  points  never  have  been  cared  for  enough  up  to  a  couple  of  years 
ago,  probably  for  want  of  the  right  conception  of  their  importance.  Some 
queer  phenomena  might  have  found  an  easy  explanation,  if  the  above  rules 
had  been  applied.  At  present  we  can  say,  that  a  freeze  up  is  a  matter  of 
the  past;  what  finishes  up  a  furnace  or  necessitates  a  blow  out,  is  either 
a  hole  burned  in  a  jacket,  which  occurs  probably  once  in  years,  or  a  leak 
sprung  in  a  coil.  Someone  of  you  gentlemen,  who  has  seen  or  had  a  more 
intimate  acquaintance  with  blast  furnaces  somewheres  else,  may  ask  for 
an  explanation  of  a  coil,  because  he  did  not  see  any  of  the  kind.  Well, 
first  this  coil  is  almost  invisible,  being  imbedded  in  the  heavy  brickwork 
of  the  upper  furnace  wall,  then  there  may  be  another  reason,  why  he  did 
not  see  it,  that  is,  because  it  actually  did  not  exist.  A  coil  is  really  a  thing 
of  the  past,  a  constructive  rudiment  of  a  century  ago.  Already  before  the 
old  D.  &  D.  smelter  was  put  up,  other  plants  had  the  coils  replaced  by 
water  jackets  running  clear  to  the  top.  Nevertheless,  when  the  fire  destroyed 
the  D.  &  D.  plant,  and  new  furnaces  were  bought,  it  was  decided  to  stick  to 
the  coils.  Some  experiments  had  been  made  with  wrongly  constructed  top 
jackets,  which  proved  a  failure,  mal-conducted  experiment  in  combination 
with  an  idea  of  the  management,  that  the  water,  running  even  through 
small  coils  would  have  a  tendency  to  freeze  up  a  furnace,  caused  such  a 


Black  Hills  Miitiixj  Men's  Association.  113 

wrong  conclusion.  Yes,  it  has  happened,  that  orders  were  given  to  turn 
the  water  off  from  a  new  coil,  because  it  seemed  to  threaten  a  freeze  up. 
It  w^as  a  saying,  that  the  coils  caused  a  loss  of  heat,  and  therefore  a  big  coil, 
which  had  been  tried  because  the  small  ones  burned  out  easily,  and  thus 
finished  the  life  of  the  furnace,  was  given  up  again.  When  I  took  charge 
of  the  mill  I  took  the  matter  up  again,  and  today  we  are  running  even  a 
bigger  coil  than  ever  was  tried  before  with  perfect  success.  At  least  by 
means  of  this  coil  we  can  now  run  a  furnace  over  six  months.  By  that  time 
there  has  accumulated  so  much  mud  in  the  lower  part  of  the  jacket,  that 
a  blow  out  is  imperative,  or  you  will  run  the  risk  of  an  explosion.  Lately 
I  have  put  in  a  contrivance,  which  will,  I  hope  overcome  also  this  obstacle 
as  it  will  afford  a  means  to  remove  any  scale  or  mud  from  the  jackets  with- 
out blowing  the  furnace  out.  If  this  works  all  right  there  would  be  nothing 
to  limit  the  life  of  a  furnace  but  a  terrible  disaster  to  the  driving  machinery. 
Small  break  downs  of  engine  or  pumps  do  not  finish  the  run  of  furnaces. 
We  have  had  last  winter  shut  downs  of  forty  hours  on  account  of  shortness 
of  supplies,  at  the  time  of  the  snow  blockade,  followed  by  other  shut  downs 
a  day  later,  which  ended  none  of  the  furnaces  concerned.  Formerly  a  shut 
down  for  some  greater  length  of  time  was  considered  almost  a  sure  disaster 
to  the  furnaces. 

I  have  spoken  so  far  only  of  the  one  department  of  the  Golden  Reward 
smelter,  which  is  at  present  running.  But  up  to  a  little  over  a  year  ago, 
there  used  to  be  in  operation  a  number  of  reverberatory  furnaces.  These 
were  put  in  when  the  Homestake  Company  shipped  their  concentrates  to 
us.  At  that  time  there  was  formed  such  a  vast  amount  of  flue  dust  from 
the  blast  furnaces  that  it  was  hardly  possible  to  run  it  over  again  through 
the  same  furnaces.  Before  the  installation  of  the  reverberatories,  however, 
it  was  tried  to  lower  the  amount  of  flue  dust  formed  from  these  fines  by 
mixing  them  with  lime  or  molasses  but  without  success.  The  reverberatories 
proved  to  be  the  best  way  of  treating  them,  though  they  caused  a  big  extra 
expense,  but  taking  the  good  effect  of  the  concentrates  on  the  furnace 
run  into  account,  it  paid  to  do  it.  At  present  we  are  not  getting  any  more 
concentrates,  and  having  only  little  flue  dust,  which  we  can  handle  easily  by 
running  it  over  again  in  the  blast  furnaces,  the  reverberatories  are  shutdown. 

These  reverberatory  furnaces  were,  however,  used  not  only  for  the  treat- 
ment of  the  flue  dust,  but  also  the  sows  formed  in  the  blast  furnaces  and 
the  forehearths,  the  amount  of  which  was  at  times  very  great,  were  handled 
in  them.  Both  the  formation  of  such  sows  to  such  an  extent  and  the 
separate  working  of  them  was  in  my  opinion  no  necessity  and  certainly 
not  a  paying  institution.  I  found  out  that  they  form,  if  judiciously  given 
back  to  the  blast  furnaces  an  excellent  material  for  keeping  the  same  in 
a  first  class  shape.  But  just  as  good  it  is  to  reduce  the  formation  of  them 
to  as  little  as  possible,  as  they  carry  a  high  value  of  gold,  which  has  t^be 
rehandled.  I  obtain  this  result  by  widening  the  furnaces  at[the  tuyere 
level.  Our  furnaces,  when  I  took  hold  of  the  plant,  were  from  thirty-four 
to  thirty-six  inches  wide,  at  present  none  is  narrower  than  forty^inches. 
This  prevents  the  reduction  of  iron  to  the  form  of  sow  sufficiently. 


114  Black  Hillx  Minimj  Men's  Association. 

Gentlemen,  having  thus  arrived  almost  at  the  end  of  our  review  of  the 
past  and  present  of  the  works,  we  have  to  enter  now  a  question,  which 
I  do  not  consider  as  settled  yet.  By  relinquishing  the  Homestake  concen- 
trates we  had  to  resort  to  a  kind  of  pyrite,  the  only  one  available  in  large 
quantities  here  in  the  Black  Hills,  but  a  very  poor  substitute  on  account 
of  its  graphitic  character.  You  all  know,  that  graphite  is  a  modification 
of  carbon,  that  requires  an  immense  temperature  to  burn  off.  In  the 
beginning  we  had  lots  of  trouble  with  them;  I  tried  to  smelt  them  prepara- 
tory in  the  reverberatories,  but  found  that  they  could  not  be  melted  at  the 
temperature  obtainable  in  such  a  furnace.  When  put  directly  into  the 
blast  furnace  in  the  shape  they  were  received  in  from  the  mine,  they  caused 
the  charges  to  become  extremely  flamy  on  top,  so  that  the  feeders  could 
hardly  do  their  work  properly.  If  then  even  the  coke  happened  to  be 
rather  dense  or  too  much  broken  up,  the  evil  was  much  more.  I  noticed 
also,  that  the  coarseness  of  the  charge  generally  had  an  unfavorable  influ- 
ence on  this  phenomena,  and  as  something  had  to  be  done,  I  decided  to 
make  some  experiments  with  crushing  the  pyrites,  which  scheme  led  at  last 
to  some  degree  of  success.  They  continue,  however,  to  be  a  hard  proposi- 
tion, not  only  on  account  of  the  fires  rising  to  the  top  once  in  a  while,  but 
the  whole  run  of  the  furnace,  if  we  compare  it  with  that  made  with  concen- 
trates, is  impeded. 

Gentlemen,  we  will  now  consider  the  improvements  that  can  be  made 
on  the  process  and  apparatus  of  the  present  plant  proper.  As  stated  above, 
the  substitution  of  a  more  suitable  kind  of  pyrite  for  the  graphite  bearing 
material  is  much  desirable,  and  the  supply,  if  possible,  should  be  increased 
to  such  an  extent,  that  no  or  nearly  no  lime  would  be  required  as  a  flux 
and  the  coke  charge  could  be  cut  down  to  about  one-half  of  the  present 
amount.  Such  a  change  would  avoid  the  addition  of  copper  ore  altogether 
and  cause  a  greater  saving  in  values.  As  to  the  apparatus,  though  little 
things  have  been  changed  gradually  with  the  run  of  lime,  as  I  have  stated, 
no  radical  changes  have  been  made. 

If  all  these  changes  are  made,  the  reduction  in  treatment  expense  will 
be  about  fifty  per  cent  of  the  present.  I  hope  that  the  next  year  will  real- 
ize some  of  them  already,  I  am  well  aware  what  a  great  responsibility 
must  be  incurred  by  the  management,  in  entering  all  these  questions  for 
adjustment,  but  enterprise  assisted  by  good  judgment  is  the  only  spring 
that  turns  the  wheel  of  chances  for  ultimate  success,  and  can  give  the  mill, 
that  has  successfully  competed  for  all  these  years  with  the  other  ore  reduc- 
tion plants,  and  outlived  some  of  them,  a  good  footing  in  the  struggle  for 
its  further  existence.  With  the  ample  supply  of  ore,  which  the  Gold«n 
Reward  Company  keeps  on  hand,  to  me  the  future  of  the  smelting  works 
looks  brighter  than  ever  before,  and  being  at  the  same  time  in  charge  of 
the  company's  cyanide  mill,  I  am  probably  in  a  position  to  weigh  off 
results  and  I  will  close  my  remarks  by  saying,  that  both  processes  promise 
to  hold  their  own  fields  here  in  the  Black  Hills. 


116  Black  Hills  Mining  Men's  Association. 

MINING  IN  THE  BALD  MOUNTAIN  AND   RUBY  BASIN  DIS- 
TRICTS OF  THE  BLACK  HILLS. 

BY  JOHN  BLATCHFORD. 
GENTLEMEN: 

In  describing  a  portion  of  this  formation  I  shall  not  touch  on  the  geo- 
logical part  of  it  because  that  has  been  gone  into  so  extensively  by  such 
men  as  Newton,  Devereaux,  Headden,  Blake,  Jenny,  Carpenter,  Hoffman, 
Farrish,  Dr.  McGillicuddy,  Rickard,  Smith,  Fulton,  O'Harra,  and  a  num- 
ber of  other  noted  men  who  have  written  some  very  good  papers  showing 
the  geological  features  of  this  part  of  the  country.  I  merely  intend  to  say 
a  few  words  on  the  occurrences  of  the  ore  bodies  as  we  find  them  in  this 
formation. 

These  ores  were  first  discovered  in  1877,  but  there  was  very  little  done 
on  them  until  1890  and  1891,  because,  up  to  this  time,  all  of  the  ore  had 
to  be  hauled  by  teams  and  shipped  out  of  the  country  to  be  treated.  In 
the  latter  part  of  the  summer  of  1891,  the  Burlington  and  the  Elkhorn 
Railroad  Companies  placed  a  number  of  spurs  into  the  different  mines; 
after  this  the  work  really  began  in  earnest. 

At  this  time  it  was  not  known  how  extensive  these  ore  bodies  would 
prove  to  be,  but  after  continuous  work  for  over  twelve  years,  now,  we  find 
that  they  are  almost  unlimited.  Ores  that  we  could  not  look  at  years  ago, 
on  account  of  their  low  grade,  can  be  handled  today,  with  our  new  reducing 
or  cyanide  process,  at  a  profit. 

Since  it  has  been  discovered  what  these  ores  can  be  treated  for  with 
this  process,  we  find  that  we  have  to  work  over  a  considerable  area  of 
that  which  has  already  been  worked.  There  is  no  doubt  but  that 
this  will  be  a  great  advantage  to  us,  in  the  future,  because  we  will  be  able 
to  take  out  our  low  grade  ore,  as  well  as  the  better  grade,  as  we  advance 
in  our  work. 

The  ore  bodies  or  chutes  are  numerous.  The  largest  bodies  so  far 
discovered,  of  the  better  grade  ore,  east  of  Bald  Mountain  and  Terry's 
Peak,  lie  on  the  quartzites,  and  these  lie  on  the  Archaen  schists  and  slates; 
this  is  what  is  known  as  the  vertical  formation.  Some  places  in  our  mines 
the  flat  ore  body  is  known  to  lay  and  to  be  intermixed  with  a  vertical  ore 
body,  which  comes  from  below,  not  showing  any  division  by  quartzites. 
It  is  one  of  those  occurrences  which  causes  me  to  believe  that  there  are  a  num- 
ber of  those  vertical  ore  bodies,  or  quartz  ledges,  that  are  covered  up,  by 
this  sedimentary  formation,  for  instance,  quite  a  portion  of  the  Homestake 
ore  bodies  have  been  more  or  less  covered  by  this  flat  formation,  but  in 
other  places  the  flat  portion  being  more  or  less  eroded,  left  the  vertical 
portion  to  be  more  easily  prospected  than  it  is  in  this  district. 

The  eastern  boundary  of  the  flat  formation  begins  at  the  original 
Golden  Reward  and  Buxton,  and  almost  at  the  base  of  Bald  Mountain 
on  the  north  and  to  the  west  of  the  Sugar  Loaf  Mountain  on  the  south. 
It  starts  with  a  thin  layer  of  quartzite,  lying  on  the  schist,  covered  with 


Black  Hills  Mining  Men's  Association.  117 

sandstone  and  shales;  it  gradually  thickens  towards  the  west,  not  so  much 
because  the  hill  rises  but  because  the  quartzite  and  schist  drop.  It  drops 
at  various  distances,  at  a  time,  until  it  gets  several  hundred  feet  below  the 
surface;  making  a  number  of  layers  of  different  material  above  it  and  on 
and  between  some  of  these  layers  is  where  we  find  what  is  called  top  con- 
tacts. 

As  we  get  nearer  Terry's  Peak  the  flat  formation  thickens  more  by  the 
rise  of  the  surface  than  by  the  fall  of  the  quartzite,  and  west  of  the  Peak  it- 
seems  to  keep  this  thickness  for  a  number  of  miles.  Towards  this  rise 
or  thickening  of  the  formation  is  where  the  top  layers  of  ore  become  more 
numerous.  How  many  layers  or  so-called  contacts  there  are  has  not  yet 
been  determined.  There  is  something  new  continually  cropping  out. 

In  these  upper  layers  we  usually  find  a  vertical  or  crack  filled  with 
ore  extending  downwards  for  hundreds  of  feet,  with  a  number  of  lense-like 
shaped  bodies  of  ore,  branching  out  at  different  intervals,  some  places  con- 
necting with  bodies  from  nearby  verticals. 

At  present  most  of  the  workings  west  of  the  Peak  are  on  the  upper 
contacts.  In  the  Ragged  Top  district  the  ore  bodies  are  up  in  the  lime  and 
they  are  proving  to  be  very  extensive  and  profitable.  Around  Portland 
they  are  all  in  shales,  scarcely  any  work  in  that  neighborhood  being  done 
on  the  quartzite  as  yet.  There  is  no  doubt  in  my  mind  when  they  commence 
to  look  for  the  lower  ore  bodies  west  of  the  Peak  but  that  they  will  find 
them  large  and  valuable  on  the  quartzite  just  the  same  as  they  occur  east 
of  the  Peak. 

The  gulches  on  the  surface  on  the  east  side  of  the  mountain  all  trend 
toward  the  east  and  on  the  west  side  towards  the  west,  but  underground 
we  find  this  different;  from  Bald  Mountain  south  it  appears  that  the  original 
channels  all  flowed  to  the  south  and  from  the  north  of  Bald  Mountain  to 
the  north.  The  water  courses  and  the  dip  of  the  quartzite  show  this  to 
be  the  case.  Present  conditions  are  exactly  the  opposite  of  the  original 
conditions.  The  original  dykes  all  have  a  north  and  south  course,  while 
a  few  of  the  later  dykes  near  the  base  of  Bald  Mountain  have  an  east  and 
west  course  and  the  ore  bodies,  or  nine-tenths  of  them,  have  a  north  and 
south  course. 

These  ore  bodies  vary  in  width  and  thickness;  we  find  some  of  them 
over  four  hundred  feet  in  width  and  various  thicknesses,  from  six  to  twenty 
feet,  and  of  various  values,  ranging  from  five  to  fifty  dollars.  The  general 
average  of  what  we  call  smelter  ores  are  about  twenty  dollars  per  ton  and 
a  general  average  of  cyanide  ores  in  the  neighborhood  of  from  eight  to 
ten  dollars  per  ton. 

To  describe  the  conditions  of  the  quartzite  we  may  compare  them  with 
the  waves  of  the  ocean.  Some  places  we  might  imagine  there  was  not 
much  wind,  making  the  quartzite  smooth  and  then  a  big  wind  lifts  the 
wave  up  from  two  to  three  hundred  feet,  the  quartzite  raises  the  same, 
some  places  we  have  one  hundred  feet,  from  that  to  two  hundred  feet  or 
more  across  the  top  of  it  going  down  some  places  almost  at  a  vertical,  or 
some  places  with  a  gradual jslope,  others  with  steps. 


118  Black  Hills  Mining  Men's  Association. 

We  find  these  ore  bodies  at  the  base,  on  the  steps  and  slopes,  most 
times  on  the  top  of  these  large  up-lifts,  but  very  seldom  find  any  ore  bodies 
in  the  channel  proper.  And  it  appears  that  the  most  of  the  level  places 
in  the  quartzites  seem  to  be  capped  with  large  sheets  of  porphyry,  but  at 
every  fault  and  in  close  proximity  with  a  fault.  The  capping  is  most  all 
composed  of  shales  and  sandrocks.  No  doubt  this  has  a  good  deal  to  do 
with  the  occurrences  of  the  ore  along  the  breaks,  those  being  in  themselves 
an  altered  condition  of  these  same  shales  and  sandrocks. 

There  is  no  question  but  that  this  flat  ore  formation  follows  the  lime 
stone  ridge  from  between  fifty  and  sixty  miles  on  the  south  and  about 
twenty-five  miles  on  the  west,  and  to  Spearfish  on  the  north. 

This  does  not  include  all  of  the  flat  formation  of  the  Black  Hills.  The 
Galena  district  has  a  very  extensive  area  of  this  formation.  The  present 
developments  there  are  very  encouraging,  although  there  has  not  been  enough 
done  to  determine  how  large  the  ore  bodies  are,  but  they  are  numerousr 
and  prospects  obtained  from  most  of  them  are  good.  There  is  still  a  very 
large  area  in  those  districts  undeveloped. 

There  is  room  for  a  good  many  mines  such  as  ours,  which  is  the 
Golden  Reward  Mining  Company's  property,  consisting  of  over  fifty  miles 
of  underground  workings,  about  two-thirds  of  this  mileage  being  on  ore 
channels,  while  the  other  third  is  cross  cutting  barren  rock  to  find  ore  chan- 
nels. After  following  some  of  these  ore  bodies  close  on  to  three  miles  we 
find  them  still  continuous. 


Black  Hillx  MiiiiiHj   Men's  Axxnciution.  119 

THE   GEOLOGY  AND   MINERALOGY   OF   THE   BLACK   HILLS 

REGION. 

BY  CLEOPHAS  C.  O'HARRA,  SOUTH  DAKOTA  SCHOOL  OF  MIXES. 

The  Black  Hills  region  is  in  many  respects  a  typical  geological  unit. 
It  lies  within  the  forks  of  the  Cheyenne  River  on  the  South  Dakota- Wyo- 
ming boundary  line,  a  much  larger  portion  of  the  area  being  within  the 
state  of  South  Dakota.  Separated  from  the  Rock}'  Mountains  to  the  west 
and  southwest  by  a  distance  of  less  than  150  miles  the  region  possesses 
many  of  the  lithologic  and  physiographic  features  of  that  great  mountain 
system. 

Structurally  the  region  is  an  elliptical,  outwardly-dipping  uplift,  the 
more  distinct  features  of  which  cover  an  area  about  100  miles  long  and 
fifty  miles  wide,  the  longer  axis  approximately  coinciding  with  the  meridian 
except  in  the  northern  portion  where  the  general  direction  is  to  the  north- 
west. By  reason  of  its  isolated  position,  its  simple  structural  features  and 
the  many  excellent  natural  and  artificial  rock  exposures,  the  history  of  the 
region  may  be  interpreted  with  a  considerable  degree  of  ease. 

The  general  system  of  drainage  is  distinctly  radial.  The  two  enclosing 
arms  of  the  Cheyenne  river  wholly  separate  the  Hills  from  other  drainage 
systems  and  receive  the  many  smaller  streams  from  the  more  elevated 
mountainous  portions,  a  high  western  limestone  plateau  being  the  main 
divide.  In  certain  places  the  rapid  erosion  of  softer  beds  has  modified 
this  general  radial  arrangement,  a  prominent  example  being  in  the  for- 
mation of  the  well-known  Red  Valley,  which  forms  a  nearly  continuous 
encircling  depression  separating  the  higher  central  portions  of  the  uplift 
from  the  distinct  but  less  elevated  cretaceous  hogback  ridges  of  the  foot 
hills 

Many  of  the  streams  continue  actively  cutting  their  beds.  Each  litho- 
logic unit  with  its  particular  and  sometimes  striking  color  yields  distinctive 
topographic  forms  dependent  upon  relative  capacity  for  resisting  erosion, 
the  result  being  that  in  many  places  features  of  rare  interest  are  produced. 
The  Harney  Peak  area  of  the  Southern  Hills  with  its  bold  pinnacles  and 
walls  of  coarse  bare  granite  rising  from  their  forest-clad  base  of  metamor- 
phosed sedimentary  rocks  presents  a  beautiful  panorama,  while  the  steep- 
walled  canyons  of  Spearfish  Creek,  and  of  Elk  Creek  in  the  Northern  Hills  t 
are  among  the  most  picturesque  that  America  can  show.  Again  to  the 
northwest  along  the  Belle  Fourche  valley  where  the  horizontal  sandstones 
and  shales  have  been  intricately  carved  by  the  various  streams,  and  where 
the  brilliant  and  varied  colors  of  the  several  formations  harmoniously 
blend  with  a  wealth  of  forest  and  pasture  overlooked  here  and  there  by  the 
stately,  somber  forms  of  porphyry  buttes,  there  is  presented  a  view  well 
worth  many  a  hardship  to  see. 

The  prominent  topographic  features  are  a  high  central  basin  of  granite 
and  metamorphic  rocks  of  Algonkiaii  age,  surrounded  in  a  concentric  man- 


120  Black  Hills  Minhty  Men'*  Association. 

ner  by  a  rugged  infacing  escarpment  of  massive,  white,  carboniferous  lime- 
stone, a  wide  depression  in  the  red  Triassic  shales  and  a  high  rim  of  Creta- 
ceous hogback  ridges  or  foot  hills.  Beyond  these  are  the  later  Cretaceous 
shale  formations  which  give  rise  to  the  nearly  level  plains.  Farther  away 
on  almost  every  side,  interrupting  the  otherwise  monotonous  approach  to 
the  Hills,  there  are  abrupt  tables  and  buttes  of  Tertiary  clays,  large  por- 
tions of  which  have  been  carved  into  forms  that  bewilder  the  imagination 
of  the  most  fanciful  observer. 

In  the  Northern  Hills  Tertiary  intrusive  rocks  have  greatly  modified 
the  general  topography,  and  in  not  a  few  instances  have  formed  prominent 
landmarks.  Terry  Peak,  situated  near  the  center  of  activity  of  intrusions, 
is  the  highest  point.  It  reaches  an  altitude  of  7,069  feet.  Some  distance 
to  the  west  of  this  is  the  Bear  Lodge  range  which  culminates  in  Warren 
Peaks,  marking  a  subordinate  but  important  center  of  Tertiary  disturbance. 
Several  isolated  igneous  peaks  differing  little  in  petrographic  and  structural 
nature  from  the  prominent  peaks  of  the  more  intricately  disturbed  dis- 
tricts, already  mentioned,  stand  as  tall  sentinels  among  the  lower  peripheral 
ridges,  chief  of  these  are  Bear  Butte,  Crow  Peak,  Black  Buttes,  Inyan  Kara, 
the  Missouri  Buttes,  and  the  justly-famed  Devil's  Tower.  The  highest 
point  within  the  entire  region,  as  it  is  also  the  highest  point  in  the  United 
States  east  of  the  Rocky  Mountains,  is  Harney  Peak.  This  is  the  culmi- 
nating peak  of  the  Harney  granite  range  in  the  Southern  Hills.  It  reaches 
a  height  of  7,216  feet.  The  surrounding  limestone  escarpment  rises  high 
above  much  of  the  inner  portion  of  the  Hills,  and  considerable  areas  of  the 
plateau  along  the  western  side  in  the  vicinity  of  Crooks  Tower  closety  ap- 
proach the  height  of  Harney  Peak.  The  mean  altitude  of  the  plains  sur- 
rounding the  Hills  is  little  more  than  3,000  feet.  The  average  elevation 
within  the  hogback  ridges  is  approximately  5,000  feet. 

The  rocks  of  the  Black  Hills  show  a  wide  range  in  age  and  character. 
Within  the  crystalline  nucleus  are  pre-Cambrian  granites,  amphibolites, 
schists,  slates,  phyllites.  and  quartzites.  Beyond  this  nucleus  are  lime- 
stones, sandstones,  shales  and  conglomerates  representing  a  nearly  complete 
sequence  from  Cambrian  to  Laramie.  Their  combined  thickness  is  ap- 
proximately 10,000  feet.  Extensive  overlaps  of  Tertiary  rocks  are  also 
present  while  Pleistocene  deposits  of  various  kinds  occur  widely  distributed 
over  the  surface  of  the  region.  Silurian  limestone  is  found  in  a  few  local- 
ities, but  is  of  little  importance.  The  presence  of  Devonian  rocks  seems 
as  yet  not  conclusively  proven.  In  the  Northern  Hills  there  are  porphyritic 
rocks  in  great  profusion.  Phonolites,  Grorudites,  Audesites,  Dacites, 
Diorites  and  Lamprophyres  are  found  and  their  recent  careful  study  has 
aroused  much  interest  among  petrographers.  To  the  prospector  and  miner 
they  are  of  interest  in  that  their  intrusion  has  greatly  influenced  mineraliza- 
tion, and  the  nature  and  distribution  of  the  igneous  masses  have  to  no  little 
extent  been  a  determining  factor  in  the  occurrence  of  ore  bodies.  Fossilif- 
erous  beds  are  common  among  the  foot  hills,  while  only  a  short  distance 
to  the  southeast  are  the  world-renowned  White  River  bad  lands,  with  their 
wealth  of  vertebrate  remains. 


1 


122  Black  Hills  Mining  Men's  Association. 

The  sedimentary  deposits  were  laid  down  subsequent  to  the  upturning 
and  metamorphism  of  the  Algonkian  rocks.  These  have  had  their  various 
characters  properly  denned  by  recent  study,  the  determined  formational 
units  receiving  appropriate  individual  names.  The  oldest  rocks  of  the 
region  are  the  slates,  schists  and  quartzites.  They  constitute  the  main 
central  area  of  the  Hills.  Their  dip  approximates  the  vertical,  while  their 
strike  corresponds  fairly  well  in  a  general  way  with  the  meridian  line.  The 
quartzites  are  usually  less  easily  eroded  than  the  slates  and  schists,  in  con- 
sequence of  which  they  not  infrequently  stand  out  with  much  prominence. 
Dark,  basic,  igneous  bands  occur  in  many  places,  their  general  occurrence 
being  such  as  to  give  the  impression  of  intercalation  conformable  to  the 
original  bedding  of  the  metamorphosed  sediments.  These  rocks  have  not 
received  careful  study,  but  they  may  be  provisionally  grouped  under  the 
name  "amphibolites."  They  are  commonly  designated  by  the  prospector 
as  diorite  or  hornblende  rock.  Intimately  associated  with  all  of  these  are 
the  granites  of  the  Southern  and  Central  Hills.  In  the  northwestern  part 
of  the  Hills  on  the  South  Dakota- Wyoming  line,  another  small  but  important 
area  of  granite  is  found.  A  distinct  feature  of  nearly  all  of  this  granite 
is  its  extremely  coarse  texture.  Its  feldspar,  quartz  and  mica,  and  even 
the  less  important  and  non-essential  constituents  may  be  frequently  found 
in  isolated  crystalline  masses  of  great  size.  The  rock  is  of  the  variety  of 
granite  known  as  pegmatite,  and  as  usual  with  pegmatite,  carries  an  abun- 
dance of  rare  and  useful  minerals.  Following  the  granites,  which  are  later 
than  the  amphibolites,  but  still  of  Algonkian  age,  there  were  110  igneous 
intrusions  until  the  Tertiary.  Then  approximately  coincident  with  the 
general  uplift  of  the  Black  Hills  region,  came  the  igneous  bodies  so  abundant 
in  the  Northern  Hills.  These,  for  want  of  a  better  collective  term,  are 
commonly  designated  as  porphyries.  They  are  generally,  although  not 
always,  of  a  distinctly  porphyritic  nature,  the  large  crystals  being  quartz, 
or  more  frequently  some  form  of  feldspar,  or  occasionally  hornblende  or 
biotite.  To  mention  all  of  the  localities  where  these  may  be  found  would 
be  a  tiresome  task.  The  following  important  mountains  must  suffice: 
Terry  Peak,  Bald  Mountain,  Elk  Mountain,  Ragged  Top,  Devil's  Tower, 
Ouster  Peak,  Bear  Butte,  Crow  Peak,  Inyan  Kara,  Sundance  Mountain, 
and  Warren  Peaks.  Less  prominent  masses  occur  in  great  profusion,  and 
few  important  gulches  of  the  region  are  free  from  good  exposures  where 
structural  details  may  be  determined  with  much  precision.  The  intrusions- 
occur  in  the  form  of  dikes,  stocks,  sills  and  laccoliths,  few  regions  in  the 
world  showing  them  in  greater  number  or  to  better  advantage.  Interme- 
diate and  connecting  stages  of  every  grade  are  found,  and  erosion  has  planed 
and  dissected  the  rock-masses  so  carefully  that  the  faithful  observer  may 
easily  read  their  meaning. 

Reviewing  and  collecting  the  foregoing  facts  with  reference  to  the 
sequence  of  occurrence  of  the  many  phenomena,  it  may  be  said  that  in 
Algonkian  time  the  schists  and  quartzites  were  deposited  as  sediments  derived 
from  some  unknown  Archaean  land-mass  lying  apparently  either  to  the 
west  or  to  the  northeast  of  the  position  now  occupied  by  the  Hills.  Later 


Black  Hills  Mining  Men's  Association.  1'23 

these  sediments  were  penetrated  by  basic  eruptives  and  subsequent  to  this 
penetration  the  sediments  as  well  as  the  basic  eruptives  were  ramified  by 
quartz  veins,  many  of  which  are  gold  bearing.  Following  the  eruption  of 
the  basic  rocks,  and  after  most  or  all  of  the  gold-bearing  quartz  veins  were 
formed,  extensive  granite  intrusions  occurred.  At  some  time  during  these 
disturbances,  great  metamorphism  took  place,  the  slates  and  the  schists 
reaching  much  the  condition  in  which  we  now  find  them.  During  the  middle 
or  latter  part  of  the  Algonkian  period,  the  sea  shallowed  and  the  land  rising 
above  the  sea,  as  an  island  reached  a  considerable  height.  The  rocks  thus 
brought  under  the  influence  of  erosive  agents,  supplied  much  or  all  of  the 
sediments  which  make  up  the  Cambrian  strata.  After  this  the  land  became 
submerged,  the  later  Paleozoic  and  the  Mesozoic  sediments  indicating  at 
first  deep  water,  followed  again  by  an  unsteady  tendency  toward  shallowing 
of  the  sea. 

Near  the  beginning  of  Tertiarj*  time,  great  disturbances  took  place. 
The  region  was  lifted  quite  above  the  sea  and  deeply  cut  by  outflowing 
streams.  Sea  conditions  disappeared,  leaving  the  land  partially  or  wholly 
surrounded  by  a  considerable  body  of  water  in  the  form  of  a  lake.  Ap- 
proximately coincident  with  these  changes,  the  porphyritic  rocks  of  the 
Northern  Hills  were  intruded  and  by  their  subsequent  denudation  and 
degradation  added  their  portion  of  sediments  to  the  surrounding  lake. 
The  lake  then  disappeared  and  upon  its  dry  bed  the  modern  streams  have 
trenched  their  way. 

The  unravelling  of  all  these  facts  is  a  matter  of  much  interest  to  one 
desirous  of  knowing  the  processes  of  nature's  activities,  and  doubly  so  to  him 
who  seeks  for  mineral  wealth.  The  Black  Hills  rank  among  the  important 
mineral  producers  of  the  country.  Among  the  ores  and  minerals  already 
productive,  or  giving  promise  of  production,  the  following  are  of  importance: 

Gold,  Mica, 

Copper,  Spodumene, 

Iron,  Building  Stone, 

Manganese,  Brick  Clays, 

Silver  and  Lead,  Gypsum, 

Tin,  Coal, 

Tungsten,  Petroleum. 
Graphite, 

Of  all  these,  gold  is  preeminently  the  chief  product.  Its  presence  may 
be  detected  in  almost  every  variety  of  rock  within  the  region,  and  workable 
bodies  of  ore  are  found  in  several  different  formations.  The  following 
classification  gives  the  various  horizons  and  indicates  the  mode  of  occur- 
rence of  the  ores: 

A .     Ores  occurring  within  the  Algonkian  rocks. 

1.  In  quartz  veins. 

2.  In  veins  of  auriferous  pyrite. 

3.  In  igneous  dikes,  sheets,  etcetera. 

4.  In  slate  breccias. 

5.  In  fissure  veins. 

6.  In  mineralized  zones. 


124  Black  Hills  Mining  Men's  Association. 

B.  Ores  occurring  within  the  Cambrian  rocks. 

7.  In  the  basal  conglomerate — "cement  ores." 

8.  In  the  slates,  sandstones  and  quartzites — "siliceous"  ores. 

C.  Ores  occurring  within  the  Carboniferous  rocks. 

9.  In  brecciated  "verticals"  in  limestone — "siliceous"  ores. 

10.  In  massive  limestone — "lime-siliceous"  ores. 

D.  Ores  occurring  within  the  Pleistocene  deposits. 

11.  In  high  level  bars — "dry"  placers. 

12.  In  present  stream  beds — "wet"  placers. 

Of  these  deposits,  the  placers,  the  cement  ores,  and  the  brecciated 
limestone  verticals  early  yielded  their  most  profitable  returns;  the  pyrite 
veins  have  been  extensively  exploited  only  as  a  source  of  fluxing  material 
for  smelting  operations,  while  the  igneous  dikes  and  sheets,  slate  breccias, 
etcetera,  although  occasionally  of  importance,  have  not  received  thorough 
attention.  The  gold-bearing  quartz  veins  are  found  throughout  the  highly 
metamorphic  area  of  the  Hills,  Custer,  Pennington  and  Lawrence  counties 
all  showing  localities  yielding  good  values.  The  ore  is  generally  free-milling, 
but  there  are  certain  important  exceptions,  the  occurrence  of  which  has 
hindered  successful  development. 

The  siliceous  and  the  lime-siliceous  ores  so  extensive  in  the  Northern 
Hills,  are  wholly  refractory.  They  occur  in  the  form  of  shoots  or  channels 
in  immediate  connection  with  nearly  vertical  fractures,  running  in  a  direc- 
tion parallel  to  the  longer  axis  of  the  shoots.  These  fractures  or  verticals, 
as  they  are  frequently  called,  are  generally  slickensided  and  frequently 
form  fault  planes  along  which  more  or  less  movement  has  occurred.  The  ore 
shoots  vary  considerably  in  shape,  but  in  the  main  are  greatly  elongated 
bodies  having  a  rounded  or  lenticular  cross-section.  They  lie  in  a  general 
north-south  direction  and,  excepting  certain  irregularities  produced  by 
lateral  branches,  are  practically  parallel  with  each  other.  The  structural 
relations  are  occasionally  complex.  Folding  is  observed,  faulting  frequently 
occurs,  and  igneous  intrusions  sometimes  aid  in  concealing  true  stratigraphic 
relations.  Usually,  however,  the  conditions  are  of  such  a  nature  as  to 
cause  no  serious  hindrance  to  the  proper  development  of  mining  property. 
The  siliceous  ores  are  found  at  various  horizons  within  the  Cambrian,  chief 
of  which  is  immediately  above  the  conglomeratic  quartzite.  The  lime- 
siliceous  ores  occur  at  various  horizons  within  the  Carboniferous,  the  chief 
position  being  near  the  top  of  the  massive  white  or  gray  limestone,  now 
technically  known  as  the  Pahasappa  formation.  Tertiary  igneous  rocks 
have  cut  and  intercolated  the  Cambrian  and  Carboniferous  strata  to  a 
marked  degree,  and  it  is  to  this  action  either  directly  or  indirectly,  that  the 
deposition  of  the  ores  is  due. 

Of  all  the  classes  of  ores  mentioned,  that  of  the  impregnated  zones 
has  longest  yielded  large  returns.  The  typical  zone,  the  Homestake  Belt, 
has  furnished  approximately  three-fourths  of  the  total  gold  output  of  the 
Hills,  and  continues  today  to  afford  more  than  one-half  the  annual  produc- 
tion. The  ore  is  chiefly  low  grade  and  occurs  in  extensive  deposits  as 
garnetiferous  amphibole  schists  highly  impregnated  with  quartz.  It  is 
largely  free-milling. 


Bf 

H 


1 


fit 


126  Black  Hills  Mining  Men's  Association. 

Of  metallic  mineral  products  other  than  gold  in  the  Hills,  copper,  iron, 
manganese  and  tin  have  received  much  attention,  but  as  yet  no  properties 
worked  for  them  have  become  steadily  productive.  Copper  is  found  chiefly 
in  the  Algonkian  rocks  and  nearly  every  portion  of  the  Hills  discloses  its 
presence.  Many  of  the  properties  are  capped  by  a  heavy  gossan,  carrying 
more  or  less  copper  and  in  various  places  where  this  gossan  cap  discloses 
considerable  quantities  of  copper  extensive  prospecting  is  being  carried  on. 
As  usual  with  such  deposits,  carbonates,  oxides,  and  the  native  metal  are 
found  near  the  surface,  while  below  sulphides  occur.  A  zone  of  enrichment 
which,  judging  from  other  regions  showing  apparently  similar  conditions, 
might  be  confidently  expected,  has  not  yet  been  disclosed.  Only  future 
extensive  prospecting  under  favorable  conditions  can  prove  conclusively 
the  actual  conditions. 

Iron  is  widely  distributed,  and  in  the  central  and  southern  Hills  in 
association  with  the  slates  and  schists,  it  has  received  some  attention.  Dis- 
tance from  ready  markets  have  thus  far  prevented  its  extensive  exploitation. 

Silver  and  lead  are  found  in  the  Algonkian  metamorphic  rocks  and  in 
the  Cambrian  and  Carboniferous  sedimentaries.  Lead  ores  associated  with 
silver  have  been  mined  at  Spokane  in  the  Central  Hills,  and  at  Carbonate 
and  Galena  in  the  Northern  Hills.  The  character  of  the  ore  bodies  in  the 
several  localities  varies  widely.  They  occur  in  the  Algonkian  in  veins,  in 
the  Cambrian  as  shoots,  and  in  the  Carboniferous  as  contact  deposits,  the 
latter  two  graduating  more  or  less  into  each  other.  In  the  Central  Hills 
the  ore  is  closely  associated  with  vein  quartz,  at  Iron  Hill  it  occupied  a 
nearly  vertical  position  along  a  porphyry  dike,  where  the  latter  cuts  the 
massive  Pahasappa  limestone.  At  Galena  the  ore  bodies  are  found  with 
the  Cambrian,  their  manner  of  occurrence  being  much  the  same  as  the 
Cambrian  siliceous  gold  ores.  They,  like  the  gold  ores,  are  impregnations 
due  to  water  which  has  gained  access  to  the  easily  replaceable  calcareous 
materials  through  numerous  vertical  cracks  or  fissures  produced  by  the 
intrusion  of  Tertiary  igneous  rocks. 

Tin  is  found  in  the  granites  and  in  the  stream  gravels  of  the  Harney 
Peak  and  the  Nigger  Hill  districts.  The  ore  occurs  in  the  form  of  cassiterite. 
Cupro-cassiterite  occurs  at  the  Etta  mine  near  Keystone,  and  stannite  has 
been  identified,  but  these  last,  aside  from  their  scientific  interest,  are  of  no 
value.  The  cassiterite  is  found  as  a  constituent  mineral  of  the  granite  in 
crystals  or  masses  of  all  sizes  up  to  occasionally  several  pounds  weight. 
The  mineral  occurs  chiefly  in  a  feldspar-muscorite  aggregate,  but  is  some- 
times found  in  a  quartz-muscorite  aggregate  or  in  quartz  or  feldspar  alone. 
The  granite  is  generally  of  a  distinctly  pegmatitic  character,  and  where 
the  tin  occurs  is  in  the  nature  of  dike  material.  The  wide  distribution  of 
the  cassiterite  is  readily  conceded,  but  the  actual  value  of  the  deposits  is  a 
much  discussed  problem,  the  nature  and  details  of  which  have  been  so 
often  touched  upon  that  there  is  no  need  in  this  paper  to  offer  opinions 
upon  the  subject.  It  is  proper  to  say,  however,  that  extensive  exploratory 
operations  are  now  being  carried  on,  the  results  of  which  are  awaited  with 
much  interest. 


Black  Hills  Mining  Men's  Association.  127 

Wolframite  or  tungsten,  as  it  is  frequently  called,  is  one  of  the  most 
recent  minerals  to  enter  the  list  of  Black  Hills  metallic  products.  This 
has  been  long  recognized  in  small  amounts  in  the  granites  in  Pennington 
and  Custer  counties,  but  four  years  ago  it  was  found  in  quantity  in  Lawrence 
county  closely  associated  with  the  Cambrian  siliceous  gold  ores.  The  chief 
occurrences  are  near  Lead  and  Yellow  creek,  from  which  places  several 
carloads  have  been  shipped. 

This  extremely  brief  review  of  the  metallic  minerals  brings  us  to  the 
non-metallic  products.  These  are  of  great  interest  and  they  might  readily 
lend  themselves  to  extended  discussion.  There  is  opportunity  here,  how- 
ever, to  give  them  little  more  than  mention.  Graphite  occurs  in  the  slates 
and  schists  in  uncertain  quantity  and  value.  Mica  in  the  Harney  Peak 
granite  area  has  long  been  worked  and  still  receives  prominent  attention. 
Spodumerie,  also  in  the  Harney  Peak  granite,  especially  near  Keystone,  is 
extensively  worked  for  its  lithia  content.  It  is  well  to  state,  and  of  interest 
to  remember  that  this  mineral  occurs  in  crystals  of  unprecedented  size  no 
other  place  in  the  world  so  far  as  known,  showing  crystals  of  any  substance 
comparable  in  size  to  the  Spodumene  crystals  of  the  Keystone  district. 
Building  stone  is  abundant.  Few  of  the  geological  formations  are  wholly 
lacking  in  materials  fairly  suitable  for  building  purposes,  and  several  of 
them  can  supply  good  stone  in  unlimited  quantity.  Thus  far  the  Dakota, 
the  Lakota,  and  the  Unkpapa  sandstones  have  received  most  attention. 
The  stone  is  readily  accessible,  is  durable  and  is  otherwise  suitable  for 
structural  purposes.  Brick  clays  and  gypsum  are  abundant  and  easily 
secured.  Coal  is  found  in  the  lower  part  of  the  Lakota  along  the  western 
and  northwestern  part  of  the  Hills  in  Wyoming,  it  having  been  mined  for 
some  years  near  Newcastle  and  at  Aladdin.  Petroleum  occurs  in  some 
quantity  in  the  Benton  shales  in  the  vicinity  of  Newcastle,  and  indications 
of  it  are  found  elsewhere  in  the  foot  hills. 

In  concluding  this  brief  summary  of  the  geology  and  mineralogy  of 
the  Black  Hills  region,  I  would  add  testimony  to  that  of  many  another 
before  me  that  the  Black  Hills  region  is  truly  a  land  of  wealth  and  beauty, 
a  most  interesting  part  of  nature's  great  storehouse  where  men  may  seek 
with  profit  the  material  necessities  of  life,  and  where  they  may  not  find 
lacking  those  things  which  gratify  the  mental  nature  and  which  tend  to 
lead  to  truer  living.  / 


128  Black  Hills  Mining  Men's  Association. 

V 

GEOLOGY  OF  SOUTH  DAKOTA. 

DR.  J.  E.  TODD,  STA.TE  GEOLOGIST. 

The  task  asked  of  me  is  to  give,  so  far  as  is  practicable  in  the  time 
allowed,  a  sketch  of  the  geology  of  our  state,  particularly  of  that  portion 
outside  of  the  Black  Hills.  The  Hills  being  more  complicated  and  not 
perfectly  explored,  I  cheerfully  leave  to  others  who  have  more  time  to  devote 
to  its  colaboration  and  presentation.  Moreover,  as  you  can  readily  under- 
stand, we  have  only  time  to  select  some  of  the  more  salient  features  of  the 
vast  amount  of  details  necessarily  connected  with  such  a  theme. 

It  will  be  my  aim  to  present  in  order  the  various  geological  formations, 
give  their  leading  characteristics,  their  extent,  and  note  their  more  import- 
ant economic  relations.  As  few  of  them  have  to  do  with  mining  enter- 
prises directly,  I  shall  assume  some  freedom  to  go  beyond  the  strict  aim 
of  the  congress  and  shall  venture  to  bring  in  a  few  facts  not  directly  connected 
with  mining. 

After  a  discussion  of  the  geologic  map  I  will  present  illustrations  of 
different  formations  by  the  help  of  the  stereopticon. 

GENERAL  STRUCTURE  OF  STATE. 

For  the  benefit  of  those  unfamiliar  with  our  state  I  make  a  few  general 
statements  which  may  seem  trite  to  those  already  acquainted  with  it. 

South  Dakota  presents  greater  range  of  altitude  and  greater  variety  of 
topography  than  any  other  state  east  of  the  Rocky  Mountains.  Its  lowest 
point,  Big  Stone  Lake,  is  967  feet  above  the  sea,  and  Harney  Peak,  its 
highest,  7,215  feet.  It  has  extensive  plains  rivaling  a  floor  in  smoothness, 
rugged  mountains  surpassing  anything  in  the  Appalachians,  buttes  rising 
like  giant  pyramids  above  the  plains,  and  weird  bad  lands,  the  veritable 
work  of  goblins. 

South  Dakota  has  also  a  greater  variety  of  geological  formations  than 
any  other  state  east  of  the  Rocky  Mountains,  presenting  a  nearly  complete 
series  from  the  oldest  to  the  youngest  rocks. 

It  has  two  centers  of  ancient  crystaline  rocks  at  opposite  ends  of  the 
state.  Around  one  nearly  all  of  the  Paleozoic  formations  circle,  and  against 
the  other  most  of  the  Mesozoic  rest,  while  the  Tertiary  rocks  lie  between, 
and  the  Quaternary  deposits  are  developed  in  wonderful  profusion  both  of 
acqueous  and  glacial  origin. 

Late  estimates  of  the  thickness  of  sedimentary  or  stratified  rocks  in 
the  state  reach  a  maximum  of  10,500  feet,  of  which  1,300  are  Palezoic, 
8,000  Mesozoic,  and  1,200  Cenozoic.  If  we  make  the  bottom  of  the  Creata- 
ceous  strata,  or  the  crest  of  the  "Hogback"  surrounding  the  Black  Hills, 
the  dividing  line,  there  will  be  about  8,000  feet  of  sedimentary  rock  outside 
of  that  limit,  and  about  2,000  inside.  In  this,  of  course,  it  will  be  under- 
stood, we  neither  include  the  schists,  granites  or  porphyries  of  the  Black 
Hills  nor  the  granites  and  quartzite  of  the  eastern  end  of  the  state,  which 


Black  Hills  Mining  Men's  Association.  129 

together  are  commonly  estimated  to  have  a  thickness  two  or  three  times 
as  great. 

The  stratified  rocks  outside  of  the  Hills  consist  mostly  of  soft  shales, 
clavs  and  sands,  though  extensive  deposits  of  sandstone  and  limestone 
appear  in  some  localities.  The  general  softness  of  the  strata  is  attested 
by  two-inch  holes  being  drilled  2,000  feet  in  depth,  and  have  hole  over 
1,000  feet  deep  drilled  and  well  finished  in  four  days. 

We  have  said  that  the  stratified  rocks  were  arranged  around  two  cen- 
ters of  chystalline  rocks,  viz:  the  Black  Hills,  which  may  be  compared 
to  the  horn  of  a  saddle,  and  the  other  the  Sioux  Falls  granite  area,  which 
runs  westward  from  the  wider  granite  area  of  Minnesota,  which  may  be 
conceived  to  form  the  back  and  ridge  of  the  saddle.  This  ridge,  which  may 
be  looked  upon  as  a  buried  mountain  range,  disappears  under  the  later 
strata  near  Mitchell,  but  is  traceable  in  wells  to  the  vicinity  of  Chamberlain 
and  will  doubtless  eventually  be  found  extending  nearly  to  the  Black  Hills. 

Upon  this  saddle-like  sub-stratum  of  granite  rocks  the  Cambrian,  Silu- 
rian, Carboniferous,  Jura-Trias  and  Cretaceous  rocks  have  been  laid  like 
blankets,  declining  to  the  north  and  the  south.  Those  preceding  the 
Cretaceous  have  been  formed  round  the  "horn,"  but  have  not  reached 
more  than  half  way  to  the  east  end  of  the  state;  they  are  exposed  only 
around  the  Hills,  and,  as  before  stated,  are  to  be  described  by  another. 

GEOLOGICAL  FORMATIONS. 

Crystalline  or  Algonkian.  Before  taking  up  the  sedimentary  rocks  we 
spend  a  few  words  upon  the  granite  of  the  eastern  part  of  the  state. 

Near  Big  Stone  Lake,  in  Minnesota,  extensive  quarries  of  granite  are 
worked.  The  stone  has  been  pronounced  equal  and  even  superior  to  New 
England  granite  for  ornamental  and  building  purposes.  The  granite  ex- 
tends across  the  line  at  Big  Stone  City,  and  there  is  an  outcrop  five  to  eight 
miles  southwest  of  that  place.  The  rock  rises  several  feet  above  the  general 
surface  and  there  is  no  reason  why  it  should  not  be  quarried,  except  its 
greater  distance  from  a  railroad.  A  plant  is  already  in  operation  at  Aber- 
deen for  working  and  polishing  the  Minnesota  rock. 

The  Sioux  Falls  granite  or  quartzite,  named  from  its  prominent  occur- 
rence at  that  point,  is  a  younger  but,  if  possible,  a  more  durable  rock.  The 
outcrops  of  this  rock  are  scattered  over  a  rudely  triangular  area  extending 
to  the  altitude  of  Dell  Rapids  on  the  east  line  of  the  state,  and  westward 
to  a  point  a  few  miles  southeast  of  Mitchell.  In  this  area  there  are  probably 
three  or  four  miles  of  naturally  exposed  surface,  mostly  in  the  valleys  of 
streams.  Such  exposures  have  been  quite  generally  worked  for  local  use, 
but  nowhere  for  exportation  except  at  Sioux  Falls,  at  east  Sioux  Falls, 
where  one  of  the  largest  quarries  is  located,  at  Jasper,  Dell  Rapids  and 
Spencer.  The  rock  is  very  hard,  strong  and  of  a  light  cheerful  color,  some- 
times of  a  mottled  gray,  but  usually  of  different  shades  of  pink  or  light 
purple.  It  is  commonly  fine-grained,  breaks  quite  evenly,  not  only  with 
the  planes  of  stratification  but  also  in  other  directions.  It  is  susceptible  of 
fine  polish  and  is  much  sought  for  ornamental  and  building  purposes. 


130  Black  Hills  Mining  Men's  Association. 

Recent,  reports  announce  that  an  extensive  outcrop  of  another  crysal- 
line  rock  has  been  found  near  Sioux  Falls.  It  is  very  handsome  diorite 
of  medium  grain,  black  and  white.  It  is  susceptible  of  fine  and  durable 
polish  and  promises  to  become  a  valuable  stone. 

.     CRETACEOUS  ROCKS. 

These  cover  nearly  the  whole  state.  Some  would  say  that  at  one  time 
they  covered  the  Black  Hills  completely,  and  all  agree  that  they  at  one 
time  covered  the  whole  of  the  eastern  end  of  the  state.  At  present  they 
cover  about  nine-tenths  of  the  state,  though  they  are  in  turn  more  than 
half  covered  with  the  Tertiary  and  Quaternary  formations.  In  their  thick- 
est development  they  may  attain  5,000  feet  or  more  near  the  Black  Hills. 
Beginning  with  the  oldest  or  lowest  formation,  the  Cretaceous  includes 
(1)  the  Dakota,  (2)  Colorado,  (3)  Montana,  and  (4)  Laramie. 

DAKOTA  CRETACEOUS. 

This  group  is  named  not  from  our  state  but  from  Dakota  City,  where 
it  was  first  studied,  which  was  then  a  pioneer  town  of  Missouri  Territory. 
The  Dakota  includes,  beginning  at  the  bottom  (1)  200  to  300  feet  of  buff 
and  gray  sandstone,  prominent  at  the  west  end  of  the  state  (Lakota),  (2) 
a  gray  limestone,  thirty  feet  thick,  locally  developed  near  Hot  Springs 
(Minnewasta),  (3)  a  formation  consisting  mostly  of  shales  of  various  color's 
thirty  to  100  feet,  (Fuson),  (4)  a  massive  buff  sandstone  which  usually 
forms  the  crest  of  the  "Hogback"  around  the  Hills,  thirty-five  to  100  feet 
thick  (Dakota  proper). 

Of  the  valuable  quarries  and  deposits  of  fire  clay  in  this  formation  I 
leave  for  others  to  speak.  It  is  more  in  order  for  me  to  dwell  on  a  natural 
product  furnished  by  this  formation,  which  easily  outranks  in  utility  if  not 
in  nominal  money  value,  any  other  natural  resource  of  the  state.  Though 
its  development  is  not  called  mining,  it  employes  much  machinery,  involves 
much  engineering,  and  employes  some  hundreds  of  men  most  of  the  time. 
Unlike  most  mining  the  product  does  not  have  to  be  brought  laboriously 
to  the  surface  but  comes  without  effort  when  once  set  free.  No,  it  is  not 
petroleum  or  gas  but  a  much  more  beneficial  element — water. 

Notice  the  position  and  relations  of  this  Dakota  formation.  It  under- 
lies four-fifths  of  the  state  and  has  similar  relations  to  the  great  plains 
generally  from  Canada  to  Texas.  It  is  overlaid  by  thick,  impervious  clays 
of  succeeding  formations.  Its  western  edge  lies  from  3,500  to  6,000  feet  high 
on  the  eastern  flank  of  the  crest  of  the  continent  and  around  all  the  moun- 
tains lying  east  of  that  range,  like  the  Black  Hills.  Here  the  water  enters 
from  the  rainfall  directly,  from  the  seepage  of  streams  which  traverse  its 
edge,  and  from'  the  other  porous  formations  which  communicate  with  it 
below  the  surface  either  by  faults  or  contact  planes.  The  eastern  edge, 
which  lies  only  1,000  to  1,200  feet  above  the  sea,  is  comparatively  closely 
sealed  up  by  the  deep  covering  of  Cretaceous  clays  and  glacial  clays,  although 
there  are  notable  springs  which  show  themselves  at  several  points  along 


Black  Hills  Mining  Men's  Association.  131 

the  James  and  Missouri  Rivers,  which  are  doubtless  outlets  from  this  deposit. 
Moreover,  the  erosion  of  the  glacial  period  and  of  more  recent  streams  have 
so  lowered  the  surface  that  one-fourth  to  one-third  of  our  state  may  obtain 
flowing'  wells  from  this  source  and  still  other  portions  may  obtain  inex- 
haustible pump  wells  with  water  near  the  surface. 

It  also,  no  doubt,  has  large  quantities  of  water  stored  within  it.  much 
of  it  possible  at  altitudes  so  high  that  it  might  keep  up  the  supply  for  some 
time  even  if  rain  and  river  should  cease. 

More  than  2,000  wells  are  now  flowing  in  the  state  and  are  being  in- 
creased by  about  300  a  year.  They  may  be  very  roughly  estimated  to 
furnish  over  70,000  gallons  a  minute,  which  would  probably  be  about  ten 
times  the  spring-time  size  of  the  Cheyenne  River  at  Edgemont.  Most  of 
these  wells  are  small,  many  an  inch  and  a  quarter  in  diameter,  and  it  is 
now  generally  recognized  that  such  wells  are  not  only  cheaper  but  more 
convenient,  more  serviceable  and  longer  lived,  that  the  large  wells,  such  as 
were  made  several  years  ago.  Most  of  the  large  wells  have  shown  a  steady 
decline,  due  probably  to  the  fact  that  they  delivered  the  water  more  rapidly 
than  it  can  gather  to  them  from  the  water-bearing  rocks.  In  some  places 
they  have  fallen  off  in  flow  and  pressure  one-quarter  to  one-third.  In  some 
narrow  areas  wells  have  ceased  to  flow,  apparently  from  local  exhaustion 
of  water.  But  on  the  other  hand,  wells  have  been  flowing  nearly  twenty 
years  and  still  have  pressures  of -sixty  to  eighty  pounds  to  the  square  inch. 
Wells  have  been  used  for  nearly  that  length  of  time  for  power,  running 
electric  lights,  flour  mills,  etc.,  and  are  still  in  use. 

In  several  of  the  wells  natural  gas  forms  an  important  ingredient.  This 
is  true  particularly  along  the  Missouri  River  from  Lyman  county  to  the 
north  line  of  the  state.  The  city  of  Pierre  from  one  or  two  wells  is  abund- 
antly supplied  for  lighting  and  for  power  for  city  purposes,  and  to  a  con- 
siderable degree  for  heating.  Three  wells  in  Sully  county,  one  in  Wai  worth 
and  one  in  Campbell,  in  fact  all  which  have  been  opened  along  this  line, 
furnish  gas  in  similar  quantities.  It  seems  not  unlikely  that  these  wells 
lie  in  the  eastern  border  of  a  gas  region  extending  possibly  as  far  west  as 
Meade  county.  It  seems  to  be  derived  mainly  from  the  same  strata  which 
furnish  the  water.  It  may  possibly  enter  the  Dakota  formation  from  the 
Carboniferous  underneath  and  may  be  originally  derived  from  extensive 
beds  of  carbonaceous  matter  deposited  along  the  eastern  shore  of  the  Car- 
•boniferous  sea. 

Lignite  is  found  frequently  in  drilling  wells  in  thin  strata,  but  so  flooded 
with  water  that  no  attempt  has  been  made  to  obtain  the  product.  Thin 
layers,  twelve  to  thirty-six  inches  in  thickness  have  been,  found  locally 
developed  near  Ponca,  Nebraska,  and  Sioux  City,  and  also  around  the 
Black  Hills.  Petrified  wood,  though  not  of  a  quality  suitable  for  ornamental 
purposes,  is  found  in  considerable  quantities  around  the  Black  Hills. 


132  Black  Hills  Mining  Men's  Association. 

COLORADO  CRETACEOUS. 

This  is  named  from  its  prominence  in  eastern  Colorado  and  includes  a 
series  of  shales  with  local  developments  of  sandstone  and  limestone,  es- 
timated by  Mr.  Darton  to  be  from  1,450  to  1,700  feet  thick  around  the 
Black  Hills,  and  it  is  from  200  to  400  feet  thick  in  the  eastern  end  of  the 
state.  This  section  is  commonly  spoken  of  as  the  Benton  from  its  great 
development  near  Ft.  Bentori  on  the  upper  Missouri.  The  Colorado  also 
includes  about  200  feet  of  chalk  and  calcareous  shale  which  Dr.  Hay  den 
called  the  Niobrara.  It  is  conspicuous  along  the  Missouri  River  from  St. 
Helena,  Nebraska,  to  the  great  bend  above  Chamberlain,  because  of  its 
whiteness  when  weathered.  It  is,  however,  often  overlooked  when  un- 
weatherecl  because  of  its  grayish  tint  resembling  the  shales  above  and 
below  it.  The  Colorado  formation  contains  two  or  three  minor  horizons 
carrying  water  and  supplying  artesian  wells  in  the  eastern  part  of  the  state,, 
but  they  need  not  be  especially  distinguished  from  those  of  the  Dakota. 

The  chalk  has  a  very  small  economic  value  as  building  stone,  for  which 
it  may  be  profitably  used  if  carefully  selected. 

Its  much  more  important  use  is  for  the  manufacture  of  Portland  cement. 
Its  fine  grain,  porous  structure,  homogeneous  character  and  easy  grinding 
make  it  admirably  adapted  for  mixing  with  clay  for  making  a  superior  grade 
of  cement.  This  is  being  extensively  used  for  buildings  and  sidewalks 
throughout  the  state.  Its  chief  factory  is  at  Yankton,  but  scores  of  such 
plants  might  be  advantageously  placed  along  the  Missouri  River  and  around 
the  Black  Hills  if  there  were  sufficient  demand. 

MONTANA  CRETACEOUS. 

This  is  composed  mainly  of  the  Pierre  shales  named  from  Ft.  Pierre, 
which  are  dark  colored  and  often  becoming  plastic  clay  when  wet.  They 
are  about  1,200  feet  thick  near  the  Black  Hills,  300  to  400  in  the  eastern 
part  of  the  state.  They  constitute  the  most  extensive  stratum  of  the 
Cretaceous,  covering  at  least  nine-tenths  of  the  state.  This  is  the  "gumbo" 
of  the  Trans-Missouri  region  and  constitutes  probably  nine-tenths  of  the 
substance  of  the  glacial  clays  east  of  the  Missouri.  Hence  it  is  a  dominant 
element  in  the  formation  of  soils  over  much  of  the  state.  It  is  rich  in  mineral 
salts  favorable  for  grains  and  grasses.  The  prairie  grasses  growing  upon  it 
are  noted  for  their  nutritive  and  fattening  qualities.  Moreover,  its  im- 
permiable  character  holds  the  limited  rainfall  near  the  surface  and  promotes 
rapid  growth  in  the  rainy  season.  Afterward  it  dries  quickly  and  com- 
pletely and  preserves  the  grass  as  a  natural  hay,  nutritious  as  grain. 

Its  plastic  character  when  wet  promotes  its  rapid  erosion  and  the 
frequent  occurrence  of  land  slides  which  have  an  important  effect  on  the 
topography  wherever  it  is  found.  It  carries  little  or  no  water,  and  if  pres- 
ent of  poor  quality. 

The  Montana  also  includes  the  Fox  Hills  formation,  150  to  300  feet  of 
shales  and  sandstone  overlying  the  Pierre.  It  may  possibly  be  a  local 


Black  Hills  Mining  Men's  Association.  133 

^development  in  the  later  Pierre.  It  caps  the  eastern  part  of  the  dividing 
.  plateaus  between  the  Cheyenne  and  Moreau  Rivers  and  also  between  the 
latter  and  the  Grand.  Its  sandy  character  forms  a  natural  mulching  for 
the  regions  where  it  extends.  Growth  of  grasses  and  crops  extends  over  a 
longer  period,  and  they  are  not  subject  to  such  extreme  draught  as  upon 
tbe  "gumbo".  Springs  are  not  infrequent,  because  of  its  attractive  fossils 
it  is  often  a  rich  field  for  the  collector. 

LARAMIE  CRETACEOUS. 

This,  in  our  state,  is  represented  by  perhaps  2,500  feet  of  sandstone, 
shales,  loams  and  clays  interstratified.  It  is  a  fresh  water  formation  unlike 
all  preceding,  which  were  marine.  It  was  formed  by  streams,  marshes  and 
lakes.  It  is  probably  thickest  in  the  northwest  corner  of  the  state,  thins 
rapidly  to  the  south  and  more  slowly  to  the  east.  Its  ragged  edge  extends 
nearly  to  the  Black  Hills  on  the  south  and  across  the  Missouri  River  along 
the  northern  line  of  the  state  where  it  appears  in  conspicuous  buttes. 

For  soil  making  it  combines  the  qualities  of  preceding  formations.  It 
frequently  exhibits  fine  springs.  It  contains  especially  in  its  upper  por- 
tions, thick  deposits  of  sandstone  which  in  time  will  be  very  valuable  for 
local  buildings. 

Undoubtedly  the  most  valuable  product  of  the  Laramie  is  lignite.  It 
has  already  attained  prominence  as  a  commercial  product  in  North  Dakota. 
There  it  is  found  in  thicker  beds  and  nearer  lines  of  transportation,  but  beds 
five  to  fifteen  feet  thick  are  not  uncommon  in  the  vicinity  of  the  Short  Pine 
Hills,  Cave  Hills  and  Slim  Buttes,  and  workable  beds  may  be  found  north 
of  a  line  extending  from  near  the  south  end  of  Slim  Buttes  to  the  head  of 
Fire  Steel  Creek,  in  northwestern  Dewey  county,  and  thence  northeast  to 
where  Oak  creek  crosses  the  north  line  of  the  state.  This  includes  an  area 
within  our  borders  of  about  5,000  square  miles. 

Lignite  differs  from  coal  in  containing  a  larger  amount  of  water,  which 
by  evaporating  causes  it  to  slack.  This  interferes  with  its  convenient  use 
as  a  fuel.  In  Germany  it  is  extensively  formed  into  briquettes  or  small 
blocks  which  form  a  superior  domestic  fuel. 

We  look  upon  the  Pierre  as  the  most  hopeful  source  of  petroleum  if  such 
be  found  within  our  borders.  We  are  led  to  this  by  the  deposits  in  our 
neighboring  state  of  Wyoming  and  by  the  fact  that  little  or  no  traces  of  oil 
have  been  found  in  the  drilling  of  the  numerous  wells  in  the  eastern  part 
of  the  state,  several  of  which  have  gone  down  to  crystalline  rock.  It  must 
not  be  assumed,  however,  that  we  have  sufficient  evidence  to  arrive  at  any 
confident  conclusion  in  this  matter. 

The  Cretaceous  was  a  time  when  reptiles  ruled  the  world.  Gigantic  and 
strange  forms  swarmed  upon  the  sea  and  land,  and  were  even  given  wings 
to  navigate  the  air.  During  Colorado  and  Montana  times  the  forms  of  life 
were  largely  marine.  In  the  Laramie  huge  land  forms  became  numerous. 
In  our  views  we  indicate  some  of  these. 


134  Black  Hills  Mining  Men's  Association. 

TERTIARY  FORMATIONS. 

These  include  light  colored  marls,  sandstones  and  clays  which  arc  so 
conspicuous  in  the  White  River  Bad  Lands.  They  are  divided  into  the  so- 
called  White  River  beds,  800  to  900  feet  thick  in  the  higher  points  around 
Pine  Ridge  and  thinning  out  in  all  directions  more  slowly  to  the  east.  There 
is  also  a  patch  in  the  vicinity  of  the  Short  Pine  Hills  and  Slim  Buttes.  Over 
these  lie  generally,  and  thicker  toward  the  east,  300  to  400  feet  of  loams 
and  marls  with  mortar-like  sandstones.  These  extend  east  of  the  Missouri 
River  in  the  southern  portion  of  the  state  in  the  more  elevated  points,  like 
the  Bijou  Hills  and  Wessington  Hills. 

The  peculiar  erosion  of  these  beds  cause  the  noted  White  River  Had 
Lands  of  which  we  show  characteristic  views.  The  deposits  are  all  of  fresh 
water  origin,  the  work  of  rivers  and  lakes  by  which  the  weathering  of  the 
mountains  on  the  west  were  spread  out  in  extensive  sheets  upon  the  plains 
on  the  east. 

In  the  Tertiary  times,  reptiles  had  passed  and  mammals  began  to  have 
their  day.  Nature  at  that  time  made  some  strange  types  which  seem  to 
have  proved  unfitting  to  continue,  but  others  have  by  transformation  lived 
on  to  the  present  and  are  now  the  esteemed  and  useful  servants  of  man — 
the  horse  here  deserves  most  prominent  mention. 

Of  economic  effects  of  these  formations,  we  may  briefly  mention  natural 
shelters  for  stock,  frequent  springs,  and  contributions  to  curiosity  shops  in 
the  way  of  fossils,  some  ornamental  stones  are  found  in  considerable  quan- 
tities— satin  spar,  moss  agate,  and  blue  chalcedony  or  sapphirine. 

Fullers'  earth  and  volcanic  ash  abound  and  will  in  time  be  counted 
valuable. 

QUARTERNARY  FORMATIONS. 

These  comprise  the  unconsolidated  deposits  which  lie  upon  the  surface 
of  other  formations  like  a  blanket  and  which  are  frequently  spoken  of  as 
drift.  The  eastern  half  of  the  state,  east  of  the  Missouri  River,  is  almost 
completely  covered  with  a  blanket  of  till  or  boulder  clay,  ten  to  200  feet  in 
thicknesss,  lying  upon  highlands  and  lowlands  alike.  Associated  with  it 
are  belts  of  stony  hills  or  moraines,  lake  beds  and  ancient  channels  are  fre- 
quent features.  Here  are  included  also  the  numerous  terraces,  some  of 
them  300  or  400  feet  above  the  present  stream,  and  sometimes  several  miles 
in  width,  covering  with  sand  and  loam  which  come  in  to  modify  the  effects 
of  the  formations  hitherto  discussed. 

These  terraces  are  particularly  prominent  along  the  western  tributaries 
of  the  Missouri,  but  are  also  conspicuous  on  that  stream  and  along  channels 
now  vacated  but  occupied  during  the  glacial  period. 

The  marked  effects  of  the  glacial  period  upon  the  geology  of  our  state 
we  need  not  dwell  upon,  but  turn  our  attention  more  to  the  economic  results 
which  many  may  overlook. 

We  sometimes  become  impressed  by  the  great  expense  necessary  to 
prepare  the  natural  surface  for  the  proper  location  of  manufacturnig  plants, 


Black  Hills  Mining  Men's  Association.  135 

irrigation  projects,  or  the  building  of  cities.  The  work  of  the  glacial  period, 
especially  in  the  eastern  half  of  the  state,  can  scarcely  be  overestimated 
from  an  economical  standpoint.  By  it  the  surface  was  smoothed  and  beau- 
tifully graded  for  agricultural  purposes,  natural  basins  were  formed  for  the 
retention  of  rainfall,  thus  giving  an  object  lesson  to  man  for  the  further 
improvement  of  the  region,  extensive  deposits  of  sand  and  gravel  were 
formed,  the  components  of  various  formations  were  intermingled  and  ground 
together  to  form  a  rich  sub-soil,  picturesque  lakes  and  pleasing  elevations 
were  formed  for  pleasure  resorts,  and  extensive  terraces  conveniently  located 
along  prominent  streams  seem  naturally  prepared  for  suitable  locations  of 
cities  and  towns. 

It  scarcely  need  be  stated  that  no  traces  of  precious  metals  have  been 
found  outside  of  the  Hills.  While  in  California  and  other  localities  gold  has 
been  found  in  Mesozoic  and  Tertiary  strata,  it  should  be  remembered  that 
it  has  always  been  in  connection  with  marked  disturbance  of  the  earth's  crust 
with  the  formation  of  veins  and  the  outflow  of  igneous  rocks.  No  such 
disturbance  has  yet  been  noted  in  our  borders.  Strata  have  been  somewhat 
tilted  in  the  Slim  Buttes  and  profound  crevices  have  been  formed  in  the 
tertiary  of  the  Bad  Lands  and  filled  with  sand,  gypsum  and  quartz,  but 
these  have  evidently  failed  to  reach  to  the  deep-seated  waters  which  are 
the  visual  vehicles  of  precious  metals. 

The  finding  of  gold  has  been  reported  from  several  localities  but  it  has 
invariably  been  found  to  rest  upon  very  superficial  evidence.  At  a  few 
points  in  the  eastern  part  of  the  state  very  minute  quantities  have  been 
found  in  the  glacial  drift,  which  may  be  reasonably  referred  to  the  region 
of  the  Lake  of  the  AVoods  as  their  probable  origin.  The  most  clear  case  of 
this  sort  was  at  Gary  several  years  ago. 

This  is  the  story  of  the  rocks  of  our  state  outside  the  Hills  so  far  as  has 
yet  been  interpreted.  It  is  full  of  promise.  Nature  has  done  her  part, 
probably  better  than  has  been  sometimes  thought.  Wherein  our  circum- 
stances are  novel  or  peculiar  a  hint  is  given  us  of  the  perculiar  destiny  to 
which  a  kind  Providence  has  called  us.  The  secret  of  commercial  and  social 
success  in  our  commonwealth  is  to  learn  the  truth  concerning  our  resources 
and  the  best  methods  of  utilizing  them  Let  us  go  on  in  an  honest,  generous 
spirit  to  make  the  most  of  them  patiently  and  hopefully,  and  to  welcome 
and  encourage  all  who  may  cast  in  their  lot  with  us. 


RETURN       CIRCULATION  DEPARTMENT 

TO«w^       202  Main  Library 

LOAN  PERIOD  1 
HOME  USE 

2 

3 

4 

5 

6 

ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 

1 -month  loans  may  be  renewed  by  calling  642-3405 

6-month  loans  may  be  recharged  by  bringing  books  to  Circulation  Desk 

Renewals  and  recharges  may  be  made  4  days  prior  to  due  date 

DUE  AS  STAMPED  BELOW 


FORM  NO.  DD  6,  40m  10 '77 


UNIVERSITY  OF  CALIFORNIA,  BERKELEY 
BERKELEY,  CA  94720 


YC  6^875 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


